# Routing

## Handlers

A Handler, as the name implies, handle requests.

```go
// A Handler responds to an HTTP request.
// It writes reply headers and data to the
// Context.ResponseWriter() and then return.
// Returning signals that the request is finished;
// it is not valid to use the Context after or
// concurrently with the completion of the Handler call.
//
// Depending on the HTTP client software, HTTP protocol version,
// and any intermediaries between the client and the iris server,
// it may not be possible to read from the
// Context.Request().Body after writing to the context.ResponseWriter().
// Cautious handlers should read the Context.Request().Body first, and then reply.
//
// Except for reading the body, handlers should not modify the provided Context.
//
// If Handler panics, the server (the caller of Handler) assumes that
// the effect of the panic was isolated to the active request.
// It recovers the panic, logs a stack trace to the server error log
// and hangs up the connection.
type Handler func(Context)
```

Once the handler is registered, we can use the returned [`Route`](https://godoc.org/github.com/kataras/iris/core/router#Route) instance to give a name to the handler registration for easier lookup in code or in templates.

For more information, checkout the [Routing and reverse lookups](routing_reverse.md) section.

## API

All HTTP methods are supported, developers can also register handlers for same paths for different methods.

The first parameter is the HTTP Method,
second parameter is the request path of the route,
third variadic parameter should contains one or more iris.Handler executed
by the registered order when a user requests for that specific resouce path from the server.

Example code:

```go
app := iris.New()

app.Handle("GET", "/contact", func(ctx iris.Context) {
    ctx.HTML("<h1> Hello from /contact </h1>")
})
```

In order to make things easier for the end-developer, iris provides functions for all HTTP Methods.
The first parameter is the request path of the route,
second variadic parameter should contains one or more iris.Handler executed
by the registered order when a user requests for that specific resouce path from the server.

Example code:

```go
app := iris.New()

// Method: "GET"
app.Get("/", handler)

// Method: "POST"
app.Post("/", handler)

// Method: "PUT"
app.Put("/", handler)

// Method: "DELETE"
app.Delete("/", handler)

// Method: "OPTIONS"
app.Options("/", handler)

// Method: "TRACE"
app.Trace("/", handler)

// Method: "CONNECT"
app.Connect("/", handler)

// Method: "HEAD"
app.Head("/", handler)

// Method: "PATCH"
app.Patch("/", handler)

// register the route for all HTTP Methods
app.Any("/", handler)

func handler(ctx iris.Context){
    ctx.Writef("Hello from method: %s and path: %s", ctx.Method(), ctx.Path())
}
```

## Grouping Routes

A set of routes that are being groupped by path prefix can (optionally) share the same middleware handlers and template layout.
A group can have a nested group too.

`.Party` is being used to group routes, developers can declare an unlimited number of (nested) groups.

Example code:

```go
app := iris.New()

users := app.Party("/users", myAuthMiddlewareHandler)

// http://localhost:8080/users/42/profile
users.Get("/{id:int}/profile", userProfileHandler)
// http://localhost:8080/users/messages/1
users.Get("/inbox/{id:int}", userMessageHandler)
```

The same could be also written using a function which accepts the child router(the Party).

```go
app := iris.New()

app.PartyFunc("/users", func(users iris.Party) {
    users.Use(myAuthMiddlewareHandler)

    // http://localhost:8080/users/42/profile
    users.Get("/{id:int}/profile", userProfileHandler)
    // http://localhost:8080/users/messages/1
    users.Get("/inbox/{id:int}", userMessageHandler)
})
```

> `id:int` is a (typed) dynamic path parameter, learn more by scrolling down.

# Dynamic Path Parameters

Iris has the easiest and the most powerful routing process you have ever meet.

At the same time,
Iris has its own interpeter(yes like a programming language)
for route's path syntax and their dynamic path parameters parsing and evaluation.
We call them "macros" for shortcut.

How? It calculates its needs and if not any special regexp needed then it just
registers the route with the low-level path syntax,
otherwise it pre-compiles the regexp and adds the necessary middleware(s). That means that you have zero performance cost compared to other routers or web frameworks.

Standard macro types for route path parameters

```sh
+------------------------+
| {param:string}         |
+------------------------+
string type
anything

+------------------------+
| {param:int}            |
+------------------------+
int type
only numbers (0-9)

+------------------------+
| {param:long}           |
+------------------------+
int64 type
only numbers (0-9)

+------------------------+
| {param:boolean}        |
+------------------------+
bool type
only "1" or "t" or "T" or "TRUE" or "true" or "True"
or "0" or "f" or "F" or "FALSE" or "false" or "False"

+------------------------+
| {param:alphabetical}   |
+------------------------+
alphabetical/letter type
letters only (upper or lowercase)

+------------------------+
| {param:file}           |
+------------------------+
file type
letters (upper or lowercase)
numbers (0-9)
underscore (_)
dash (-)
point (.)
no spaces ! or other character

+------------------------+
| {param:path}           |
+------------------------+
path type
anything, should be the last part, more than one path segment,
i.e: /path1/path2/path3 , ctx.Params().Get("param") == "/path1/path2/path3"
```

If type is missing then parameter's type is defaulted to string, so
`{param} == {param:string}`.

If a function not found on that type then the `string` macro type's functions are being used.

Besides the fact that iris provides the basic types and some default "macro funcs"
you are able to register your own too!.

Register a named path parameter function

```go
app.Macros().Int.RegisterFunc("min", func(argument int) func(paramValue string) bool {
    // [...]
    return true 
    // -> true means valid, false means invalid fire 404 or if "else 500" is appended to the macro syntax then internal server error.
})
```

At the `func(argument ...)` you can have any standard type, it will be validated before the server starts so don't care about any performance cost there, the only thing it runs at serve time is the returning `func(paramValue string) bool`.

```go
{param:string equal(iris)} , "iris" will be the argument here:
app.Macros().String.RegisterFunc("equal", func(argument string) func(paramValue string) bool {
    return func(paramValue string){ return argument == paramValue }
})
```

Example Code:

```go
app := iris.New()
// you can use the "string" type which is valid for a single path parameter that can be anything.
app.Get("/username/{name}", func(ctx iris.Context) {
    ctx.Writef("Hello %s", ctx.Params().Get("name"))
}) // type is missing = {name:string}

// Let's register our first macro attached to int macro type.
// "min" = the function
// "minValue" = the argument of the function
// func(string) bool = the macro's path parameter evaluator, this executes in serve time when
// a user requests a path which contains the :int macro type with the min(...) macro parameter function.
app.Macros().Int.RegisterFunc("min", func(minValue int) func(string) bool {
    // do anything before serve here [...]
    // at this case we don't need to do anything
    return func(paramValue string) bool {
        n, err := strconv.Atoi(paramValue)
        if err != nil {
            return false
        }
        return n >= minValue
    }
})

// http://localhost:8080/profile/id>=1
// this will throw 404 even if it's found as route on : /profile/0, /profile/blabla, /profile/-1
// macro parameter functions are optional of course.
app.Get("/profile/{id:int min(1)}", func(ctx iris.Context) {
    // second parameter is the error but it will always nil because we use macros,
    // the validaton already happened.
    id, _ := ctx.Params().GetInt("id")
    ctx.Writef("Hello id: %d", id)
})

// to change the error code per route's macro evaluator:
app.Get("/profile/{id:int min(1)}/friends/{friendid:int min(1) else 504}", func(ctx iris.Context) {
    id, _ := ctx.Params().GetInt("id")
    friendid, _ := ctx.Params().GetInt("friendid")
    ctx.Writef("Hello id: %d looking for friend id: ", id, friendid)
}) // this will throw e 504 error code instead of 404 if all route's macros not passed.

// http://localhost:8080/game/a-zA-Z/level/0-9
// remember, alphabetical is lowercase or uppercase letters only.
app.Get("/game/{name:alphabetical}/level/{level:int}", func(ctx iris.Context) {
    ctx.Writef("name: %s | level: %s", ctx.Params().Get("name"), ctx.Params().Get("level"))
})

// let's use a trivial custom regexp that validates a single path parameter
// which its value is only lowercase letters.

// http://localhost:8080/lowercase/anylowercase
app.Get("/lowercase/{name:string regexp(^[a-z]+)}", func(ctx iris.Context) {
    ctx.Writef("name should be only lowercase, otherwise this handler will never executed: %s", ctx.Params().Get("name"))
})

// http://localhost:8080/single_file/app.js
app.Get("/single_file/{myfile:file}", func(ctx iris.Context) {
    ctx.Writef("file type validates if the parameter value has a form of a file name, got: %s", ctx.Params().Get("myfile"))
})

// http://localhost:8080/myfiles/any/directory/here/
// this is the only macro type that accepts any number of path segments.
app.Get("/myfiles/{directory:path}", func(ctx iris.Context) {
    ctx.Writef("path type accepts any number of path segments, path after /myfiles/ is: %s", ctx.Params().Get("directory"))
})

app.Run(iris.Addr(":8080"))
}
```

A **path parameter name should contain only alphabetical letters. Symbols like  '_' and numbers are NOT allowed**.

Last, do not confuse `ctx.Params()` with `ctx.Values()`.
Path parameter's values goes to `ctx.Params()` and context's local storage
that can be used to communicate between handlers and middleware(s) goes to
`ctx.Values()`.

# Routing and reverse lookups

As mentioned in the [Handlers](handlers.md) chapter, Iris provides several handler registration methods, each of which returns a [`Route`](https://godoc.org/github.com/kataras/iris/core/router#Route) instance.

## Route naming

Route naming is easy, since we just call the returned `*Route` with a `Name` field to define a name:

```go
package main

import (
    "github.com/kataras/iris"
)

func main() {
    app := iris.New()
    // define a function
    h := func(ctx iris.Context) {
        ctx.HTML("<b>Hi</b1>")
    }

    // handler registration and naming
    home := app.Get("/", h)
    home.Name = "home"
    // or
    app.Get("/about", h).Name = "about"
    app.Get("/page/{id}", h).Name = "page"

    app.Run(iris.Addr(":8080"))
}
```

## Route reversing AKA generating URLs from the route name

When we register the handlers for a specific path, we get the ability to create URLs based on the structured data we pass to Iris. In the example above, we've named three routers, one of which even takes parameters. If we're using the default `html/template` view engine, we can use a simple action to reverse the routes (and generae actual URLs):

```sh
Home: {{ urlpath "home" }}
About: {{ urlpath "about" }}
Page 17: {{ urlpath "page" "17" }}
```

Above code would generate the following output:

```sh
Home: http://localhost:8080/ 
About: http://localhost:8080/about
Page 17: http://localhost:8080/page/17
```

## Using route names in code

We can use the following methods/functions to work with named routes (and their parameters):

* [`GetRoutes`](https://godoc.org/github.com/kataras/iris/core/router#APIBuilder.GetRoutes) function to get all registered routes
* [`GetRoute(routeName string)`](https://godoc.org/github.com/kataras/iris/core/router#APIBuilder.GetRoute) method to retrieve a route by name
* [`URL(routeName string, paramValues ...interface{})`](https://godoc.org/github.com/kataras/iris/core/router#RoutePathReverser.URL) method to generate url string based on supplied parameters
* [`Path(routeName string, paramValues ...interface{}`](https://godoc.org/github.com/kataras/iris/core/router#RoutePathReverser.Path) method to generate just the path (without host and protocol) portion of the URL based on provided values

## Examples

Check out the [https://github.com/kataras/iris/tree/master/_examples/view/template_html_4](https://github.com/kataras/iris/tree/master/_examples/view/template_html_4) example for more details.

# Middleware

When we talk about Middleware in Iris we're talking about running code before and/or after our main handler code in a HTTP request lifecycle. For example, logging middleware might write the incoming request details to a log, then call the handler code, before writing details about the response to the log. One of the cool things about middleware is that these units are extremely flexible and reusable.

A middleware is just a **Handler** form of `func(ctx iris.Context)`, the middleware is being executed when the previous middleware calls the `ctx.Next()`, this can be used for authentication, i.e: if logged in then `ctx.Next()` otherwise fire an error response. 

## Writing a middleware

```go
package main

import "github.com/kataras/iris"

func main() {
    app := iris.New()
    app.Get("/", before, mainHandler, after)
    app.Run(iris.Addr(":8080"))
}

func before(ctx iris.Context) {
    shareInformation := "this is a sharable information between handlers"

    requestPath := ctx.Path()
    println("Before the mainHandler: " + requestPath)

    ctx.Values().Set("info", shareInformation)
    ctx.Next() // execute the next handler, in this case the main one.
}

func after(ctx iris.Context) {
    println("After the mainHandler")
}

func mainHandler(ctx iris.Context) {
    println("Inside mainHandler")

    // take the info from the "before" handler.
    info := ctx.Values().GetString("info")

    // write something to the client as a response.
    ctx.HTML("<h1>Response</h1>")
    ctx.HTML("<br/> Info: " + info)

    ctx.Next() // execute the "after".
}
```

```bash
$ go run main.go # and navigate to the http://localhost:8080
Now listening on: http://localhost:8080
Application started. Press CTRL+C to shut down.
Before the mainHandler: /
Inside mainHandler
After the mainHandler
```

### Globally

```go
package main

import "github.com/kataras/iris"

func main() {
    app := iris.New()
    // register the "before" handler as the first handler which will be executed
    // on all domain's routes.
    // or use the `UseGlobal` to register a middleware which will fire across subdomains.
    app.Use(before)
    // register the "after" handler as the last handler which will be executed
    // after all domain's routes' handler(s).
    app.Done(after)

    // register our routes.
    app.Get("/", indexHandler)
    app.Get("/contact", contactHandler)

    app.Run(iris.Addr(":8080"))
}

func before(ctx iris.Context) {
     // [...]
}

func after(ctx iris.Context) {
    // [...]
}

func indexHandler(ctx iris.Context) {
    // write something to the client as a response.
    ctx.HTML("<h1>Index</h1>")

    ctx.Next() // execute the "after" handler registered via `Done`.
}

func contactHandler(ctx iris.Context) {
    // write something to the client as a response.
    ctx.HTML("<h1>Contact</h1>")

    ctx.Next() // execute the "after" handler registered via `Done`.
}
```

## [Explore](https://github.com/kataras/iris/tree/master/middleware)

# Wrapping the Router

**Very rare**, you may never need that but it's here in any case you need it.

There are times you need to override or decide whether the Router will be executed on an incoming request. If you've any previous experience with the `net/http` and other web frameworks this function will be familiar with you (it has the form of a net/http middleware, but instead of accepting the next handler it accepts the Router as a function to be executed or not).

```go
// WrapperFunc is used as an expected input parameter signature
// for the WrapRouter. It's a "low-level" signature which is compatible
// with the net/http.
// It's being used to run or no run the router based on a custom logic.
type WrapperFunc func(w http.ResponseWriter, r *http.Request, firstNextIsTheRouter http.HandlerFunc)

// WrapRouter adds a wrapper on the top of the main router.
// Usually it's useful for third-party middleware
// when need to wrap the entire application with a middleware like CORS.
//
// Developers can add more than one wrappers,
// those wrappers' execution comes from last to first.
// That means that the second wrapper will wrap the first, and so on.
//
// Before build.
func WrapRouter(wrapperFunc WrapperFunc)
```

Iris' router searches for its routes based on the `HTTP Method` a Router Wrapper can override that behavior and execute custom code.

Example Code:

```go
package main

import (
    "net/http"
    "strings"

    "github.com/kataras/iris"
)

// In this example you'll just see one use case of .WrapRouter.
// You can use the .WrapRouter to add custom logic when or when not the router should
// be executed in order to execute the registered routes' handlers.
//
// To see how you can serve files on root "/" without a custom wrapper
// just navigate to the "file-server/single-page-application" example.
//
// This is just for the proof of concept, you can skip this tutorial if it's too much for you.


func main() {
    app := iris.New()

    app.OnErrorCode(iris.StatusNotFound, func(ctx iris.Context) {
        ctx.HTML("<b>Resource Not found</b>")
    })

    app.Get("/", func(ctx iris.Context) {
        ctx.ServeFile("./public/index.html", false)
    })

    app.Get("/profile/{username}", func(ctx iris.Context) {
        ctx.Writef("Hello %s", ctx.Params().Get("username"))
    })

    // serve files from the root "/", if we used .StaticWeb it could override
    // all the routes because of the underline need of wildcard.
    // Here we will see how you can by-pass this behavior
    // by creating a new file server handler and
    // setting up a wrapper for the router(like a "low-level" middleware)
    // in order to manually check if we want to process with the router as normally
    // or execute the file server handler instead.

    // use of the .StaticHandler
    // which is the same as StaticWeb but it doesn't
    // registers the route, it just returns the handler.
    fileServer := app.StaticHandler("./public", false, false)

    // wrap the router with a native net/http handler.
    // if url does not contain any "." (i.e: .css, .js...)
    // (depends on the app , you may need to add more file-server exceptions),
    // then the handler will execute the router that is responsible for the
    // registered routes (look "/" and "/profile/{username}")
    // if not then it will serve the files based on the root "/" path.
    app.WrapRouter(func(w http.ResponseWriter, r *http.Request, router http.HandlerFunc) {
        path := r.URL.Path
        // Note that if path has suffix of "index.html" it will auto-permant redirect to the "/",
        // so our first handler will be executed instead.

        if !strings.Contains(path, ".") { 
            // if it's not a resource then continue to the router as normally. <-- IMPORTANT
            router(w, r)
            return
        }
        // acquire and release a context in order to use it to execute
        // our file server
        // remember: we use net/http.Handler because here we are in the "low-level", before the router itself.
        ctx := app.ContextPool.Acquire(w, r)
        fileServer(ctx)
        app.ContextPool.Release(ctx)
    })

    // http://localhost:8080
    // http://localhost:8080/index.html
    // http://localhost:8080/app.js
    // http://localhost:8080/css/main.css
    // http://localhost:8080/profile/anyusername
    app.Run(iris.Addr(":8080"))

    // Note: In this example we just saw one use case,
    // you may want to .WrapRouter or .Downgrade in order to bypass the iris' default router, i.e:
    // you can use that method to setup custom proxies too.
    //
    // If you just want to serve static files on other path than root
    // you can just use the StaticWeb, i.e:
    // 					     .StaticWeb("/static", "./public")
    // ________________________________requestPath, systemPath
}
```

There is not much to say here, it's just a function wrapper which accepts the native response writer and request and the next handler which is the Iris' Router itself, it's being or not executed whether is called or not, **it's a middleware for the whole Router**.

# Error handlers

You can define your own handlers when a specific http error code occurs.

> Error codes are the http status codes that are bigger or equal to 400, like 404 not found and 500 internal server.

Example code:

```go
package main

import "github.com/kataras/iris"

func main(){
    app := iris.New()
    app.OnErrorCode(iris.StatusNotFound, notFound)
    app.OnErrorCode(iris.StatusInternalServerError, internalServerError)
    // to register a handler for all status codes >=400:
    // app.OnAnyErrorCode(handler)
    app.Get("/", index)
    app.Run(iris.Addr(":8080"))
}

func notFound(ctx iris.Context) {
    // when 404 then render the template $views_dir/errors/404.html
    ctx.View("errors/404.html")
}

func internalServerError(ctx iris.Context) {
    ctx.WriteString("Oups something went wrong, try again")
}

func index(ctx context.Context) {
    ctx.View("index.html")
}
```

# Context Outline

The `iris.Context` source code can be found [here](https://github.com/kataras/iris/blob/master/context/context.go). Keep note using an IDE/Editors with `auto-complete` feature will help you a lot.

```go
// Context is the midle-man server's "object" for the clients.
//
// A New context is being acquired from a sync.Pool on each connection.
// The Context is the most important thing on the iris's http flow.
//
// Developers send responses to the client's request through a Context.
// Developers get request information from the client's request a Context.
//
// This context is an implementation of the context.Context sub-package.
// context.Context is very extensible and developers can override
// its methods if that is actually needed.
type Context interface {
    // ResponseWriter returns an http.ResponseWriter compatible response writer, as expected.
    ResponseWriter() ResponseWriter
    // ResetResponseWriter should change or upgrade the Context's ResponseWriter.
    ResetResponseWriter(ResponseWriter)

    // Request returns the original *http.Request, as expected.
    Request() *http.Request

    // SetCurrentRouteName sets the route's name internally,
    // in order to be able to find the correct current "read-only" Route when
    // end-developer calls the `GetCurrentRoute()` function.
    // It's being initialized by the Router, if you change that name
    // manually nothing really happens except that you'll get other
    // route via `GetCurrentRoute()`.
    // Instead, to execute a different path
    // from this context you should use the `Exec` function
    // or change the handlers via `SetHandlers/AddHandler` functions.
    SetCurrentRouteName(currentRouteName string)
    // GetCurrentRoute returns the current registered "read-only" route that
    // was being registered to this request's path.
    GetCurrentRoute() RouteReadOnly

    // AddHandler can add handler(s)
    // to the current request in serve-time,
    // these handlers are not persistenced to the router.
    //
    // Router is calling this function to add the route's handler.
    // If AddHandler called then the handlers will be inserted
    // to the end of the already-defined route's handler.
    //
    AddHandler(...Handler)
    // SetHandlers replaces all handlers with the new.
    SetHandlers(Handlers)
    // Handlers keeps tracking of the current handlers.
    Handlers() Handlers

    // HandlerIndex sets the current index of the
    // current context's handlers chain.
    // If -1 passed then it just returns the
    // current handler index without change the current index.rns that index, useless return value.
    //
    // Look Handlers(), Next() and StopExecution() too.
    HandlerIndex(n int) (currentIndex int)
    // HandlerName returns the current handler's name, helpful for debugging.
    HandlerName() string
    // Next calls all the next handler from the handlers chain,
    // it should be used inside a middleware.
    //
    // Note: Custom context should override this method in order to be able to pass its own context.Context implementation.
    Next()
    // NextHandler returns(but it is NOT executes) the next handler from the handlers chain.
    //
    // Use .Skip() to skip this handler if needed to execute the next of this returning handler.
    NextHandler() Handler
    // Skip skips/ignores the next handler from the handlers chain,
    // it should be used inside a middleware.
    Skip()
    // StopExecution if called then the following .Next calls are ignored.
    StopExecution()
    // IsStopped checks and returns true if the current position of the Context is 255,
    // means that the StopExecution() was called.
    IsStopped() bool

    //  +------------------------------------------------------------+
    //  | Current "user/request" storage                             |
    //  | and share information between the handlers - Values().     |
    //  | Save and get named path parameters - Params()              |
    //  +------------------------------------------------------------+

    // Params returns the current url's named parameters key-value storage.
    // Named path parameters are being saved here.
    // This storage, as the whole Context, is per-request lifetime.
    Params() *RequestParams

    // Values returns the current "user" storage.
    // Named path parameters and any optional data can be saved here.
    // This storage, as the whole Context, is per-request lifetime.
    //
    // You can use this function to Set and Get local values
    // that can be used to share information between handlers and middleware.
    Values() *memstore.Store
    // Translate is the i18n (localization) middleware's function,
    // it calls the Get("translate") to return the translated value.
    //
    // Example: https://github.com/kataras/iris/tree/master/_examples/miscellaneous/i18n
    Translate(format string, args ...interface{}) string

    //  +------------------------------------------------------------+
    //  | Path, Host, Subdomain, IP, Headers etc...                  |
    //  +------------------------------------------------------------+

    // Method returns the request.Method, the client's http method to the server.
    Method() string
    // Path returns the full request path,
    // escaped if EnablePathEscape config field is true.
    Path() string
    // RequestPath returns the full request path,
    // based on the 'escape'.
    RequestPath(escape bool) string

    // Host returns the host part of the current url.
    Host() string
    // Subdomain returns the subdomain of this request, if any.
    // Note that this is a fast method which does not cover all cases.
    Subdomain() (subdomain string)
    // RemoteAddr tries to parse and return the real client's request IP.
    //
    // Based on allowed headers names that can be modified from Configuration.RemoteAddrHeaders.
    //
    // If parse based on these headers fail then it will return the Request's `RemoteAddr` field
    // which is filled by the server before the HTTP handler.
    //
    // Look `Configuration.RemoteAddrHeaders`,
    //      `Configuration.WithRemoteAddrHeader(...)`,
    //      `Configuration.WithoutRemoteAddrHeader(...)` for more.
    RemoteAddr() string
    // GetHeader returns the request header's value based on its name.
    GetHeader(name string) string
    // IsAjax returns true if this request is an 'ajax request'( XMLHttpRequest)
    //
    // There is no a 100% way of knowing that a request was made via Ajax.
    // You should never trust data coming from the client, they can be easily overcome by spoofing.
    //
    // Note that "X-Requested-With" Header can be modified by any client(because of "X-"),
    // so don't rely on IsAjax for really serious stuff,
    // try to find another way of detecting the type(i.e, content type),
    // there are many blogs that describe these problems and provide different kind of solutions,
    // it's always depending on the application you're building,
    // this is the reason why this `IsAjax`` is simple enough for general purpose use.
    //
    // Read more at: https://developer.mozilla.org/en-US/docs/AJAX
    // and https://xhr.spec.whatwg.org/
    IsAjax() bool

    //  +------------------------------------------------------------+
    //  | Response Headers helpers                                   |
    //  +------------------------------------------------------------+

    // Header adds a header to the response writer.
    Header(name string, value string)

    // ContentType sets the response writer's header key "Content-Type" to the 'cType'.
    ContentType(cType string)
    // GetContentType returns the response writer's header value of "Content-Type"
    // which may, setted before with the 'ContentType'.
    GetContentType() string

    // StatusCode sets the status code header to the response.
    // Look .GetStatusCode too.
    StatusCode(statusCode int)
    // GetStatusCode returns the current status code of the response.
    // Look StatusCode too.
    GetStatusCode() int

    // Redirect redirect sends a redirect response the client
    // accepts 2 parameters string and an optional int
    // first parameter is the url to redirect
    // second parameter is the http status should send, default is 302 (StatusFound),
    // you can set it to 301 (Permant redirect), if that's nessecery
    Redirect(urlToRedirect string, statusHeader ...int)

    //  +------------------------------------------------------------+
    //  | Various Request and Post Data                              |
    //  +------------------------------------------------------------+

    // URLParam returns the get parameter from a request , if any.
    URLParam(name string) string
    // URLParamInt returns the url query parameter as int value from a request,
    // returns an error if parse failed.
    URLParamInt(name string) (int, error)
    // URLParamInt64 returns the url query parameter as int64 value from a request,
    // returns an error if parse failed.
    URLParamInt64(name string) (int64, error)
    // URLParams returns a map of GET query parameters separated by comma if more than one
    // it returns an empty map if nothing found.
    URLParams() map[string]string

    // FormValue returns a single form value by its name/key
    FormValue(name string) string
    // FormValues returns all post data values with their keys
    // form data, get, post & put query arguments
    //
    // NOTE: A check for nil is necessary.
    FormValues() map[string][]string
    // PostValue returns a form's only-post value by its name,
    // same as Request.PostFormValue.
    PostValue(name string) string
    // FormFile returns the first file for the provided form key.
    // FormFile calls ctx.Request.ParseMultipartForm and ParseForm if necessary.
    //
    // same as Request.FormFile.
    FormFile(key string) (multipart.File, *multipart.FileHeader, error)

    //  +------------------------------------------------------------+
    //  | Custom HTTP Errors                                         |
    //  +------------------------------------------------------------+

    // NotFound emits an error 404 to the client, using the specific custom error error handler.
    // Note that you may need to call ctx.StopExecution() if you don't want the next handlers
    // to be executed. Next handlers are being executed on iris because you can alt the
    // error code and change it to a more specific one, i.e
    // users := app.Party("/users")
    // users.Done(func(ctx context.Context){ if ctx.StatusCode() == 400 { /*  custom error code for /users */ }})
    NotFound()

    //  +------------------------------------------------------------+
    //  | Body Readers                                               |
    //  +------------------------------------------------------------+

    // SetMaxRequestBodySize sets a limit to the request body size
    // should be called before reading the request body from the client.
    SetMaxRequestBodySize(limitOverBytes int64)

    // UnmarshalBody reads the request's body and binds it to a value or pointer of any type
    // Examples of usage: context.ReadJSON, context.ReadXML.
    UnmarshalBody(v interface{}, unmarshaler Unmarshaler) error
    // ReadJSON reads JSON from request's body and binds it to a value of any json-valid type.
    ReadJSON(jsonObject interface{}) error
    // ReadXML reads XML from request's body and binds it to a value of any xml-valid type.
    ReadXML(xmlObject interface{}) error
    // ReadForm binds the formObject  with the form data
    // it supports any kind of struct.
    ReadForm(formObject interface{}) error

    //  +------------------------------------------------------------+
    //  | Body (raw) Writers                                         |
    //  +------------------------------------------------------------+

    // Write writes the data to the connection as part of an HTTP reply.
    //
    // If WriteHeader has not yet been called, Write calls
    // WriteHeader(http.StatusOK) before writing the data. If the Header
    // does not contain a Content-Type line, Write adds a Content-Type set
    // to the result of passing the initial 512 bytes of written data to
    // DetectContentType.
    //
    // Depending on the HTTP protocol version and the client, calling
    // Write or WriteHeader may prevent future reads on the
    // Request.Body. For HTTP/1.x requests, handlers should read any
    // needed request body data before writing the response. Once the
    // headers have been flushed (due to either an explicit Flusher.Flush
    // call or writing enough data to trigger a flush), the request body
    // may be unavailable. For HTTP/2 requests, the Go HTTP server permits
    // handlers to continue to read the request body while concurrently
    // writing the response. However, such behavior may not be supported
    // by all HTTP/2 clients. Handlers should read before writing if
    // possible to maximize compatibility.
    Write(body []byte) (int, error)
    // Writef formats according to a format specifier and writes to the response.
    //
    // Returns the number of bytes written and any write error encountered.
    Writef(format string, args ...interface{}) (int, error)
    // WriteString writes a simple string to the response.
    //
    // Returns the number of bytes written and any write error encountered.
    WriteString(body string) (int, error)
    // WriteWithExpiration like Write but it sends with an expiration datetime
    // which is refreshed every package-level `StaticCacheDuration` field.
    WriteWithExpiration(body []byte, modtime time.Time) (int, error)
    // StreamWriter registers the given stream writer for populating
    // response body.
    //
    // Access to context's and/or its' members is forbidden from writer.
    //
    // This function may be used in the following cases:
    //
    //     * if response body is too big (more than iris.LimitRequestBodySize(if setted)).
    //     * if response body is streamed from slow external sources.
    //     * if response body must be streamed to the client in chunks.
    //     (aka `http server push`).
    //
    // receives a function which receives the response writer
    // and returns false when it should stop writing, otherwise true in order to continue
    StreamWriter(writer func(w io.Writer) bool)

    //  +------------------------------------------------------------+
    //  | Body Writers with compression                              |
    //  +------------------------------------------------------------+
    // ClientSupportsGzip retruns true if the client supports gzip compression.
    ClientSupportsGzip() bool
    // WriteGzip accepts bytes, which are compressed to gzip format and sent to the client.
    // returns the number of bytes written and an error ( if the client doesn' supports gzip compression)
    //
    // This function writes temporary gzip contents, the ResponseWriter is untouched.
    WriteGzip(b []byte) (int, error)
    // TryWriteGzip accepts bytes, which are compressed to gzip format and sent to the client.
    // If client does not supprots gzip then the contents are written as they are, uncompressed.
    //
    // This function writes temporary gzip contents, the ResponseWriter is untouched.
    TryWriteGzip(b []byte) (int, error)
    // GzipResponseWriter converts the current response writer into a response writer
    // which when its .Write called it compress the data to gzip and writes them to the client.
    //
    // Can be also disabled with its .Disable and .ResetBody to rollback to the usual response writer.
    GzipResponseWriter() *GzipResponseWriter
    // Gzip enables or disables (if enabled before) the gzip response writer,if the client
    // supports gzip compression, so the following response data will
    // be sent as compressed gzip data to the client.
    Gzip(enable bool)

    //  +------------------------------------------------------------+
    //  | Rich Body Content Writers/Renderers                        |
    //  +------------------------------------------------------------+

    // ViewLayout sets the "layout" option if and when .View
    // is being called afterwards, in the same request.
    // Useful when need to set or/and change a layout based on the previous handlers in the chain.
    //
    // Note that the 'layoutTmplFile' argument can be setted to iris.NoLayout || view.NoLayout
    // to disable the layout for a specific view render action,
    // it disables the engine's configuration's layout property.
    //
    // Look .ViewData and .View too.
    //
    // Example: https://github.com/kataras/iris/tree/master/_examples/view/context-view-data/
    ViewLayout(layoutTmplFile string)

    // ViewData saves one or more key-value pair in order to be passed if and when .View
    // is being called afterwards, in the same request.
    // Useful when need to set or/and change template data from previous hanadlers in the chain.
    //
    // If .View's "binding" argument is not nil and it's not a type of map
    // then these data are being ignored, binding has the priority, so the main route's handler can still decide.
    // If binding is a map or context.Map then these data are being added to the view data
    // and passed to the template.
    //
    // After .View, the data are not destroyed, in order to be re-used if needed (again, in the same request as everything else),
    // to clear the view data, developers can call:
    // ctx.Set(ctx.Application().ConfigurationReadOnly().GetViewDataContextKey(), nil)
    //
    // If 'key' is empty then the value is added as it's (struct or map) and developer is unable to add other value.
    //
    // Look .ViewLayout and .View too.
    //
    // Example: https://github.com/kataras/iris/tree/master/_examples/view/context-view-data/
    ViewData(key string, value interface{})

    // GetViewData returns the values registered by `context#ViewData`.
    // The return value is `map[string]interface{}`, this means that
    // if a custom struct registered to ViewData then this function
    // will try to parse it to map, if failed then the return value is nil
    // A check for nil is always a good practise if different
    // kind of values or no data are registered via `ViewData`.
    //
    // Similarly to `viewData := ctx.Values().Get("iris.viewData")` or
    // `viewData := ctx.Values().Get(ctx.Application().ConfigurationReadOnly().GetViewDataContextKey())`.
    GetViewData() map[string]interface{}

    // View renders templates based on the adapted view engines.
    // First argument accepts the filename, relative to the view engine's Directory,
    // i.e: if directory is "./templates" and want to render the "./templates/users/index.html"
    // then you pass the "users/index.html" as the filename argument.
    //
    // Look: .ViewData and .ViewLayout too.
    //
    // Examples: https://github.com/kataras/iris/tree/master/_examples/view/
    View(filename string) error

    // Binary writes out the raw bytes as binary data.
    Binary(data []byte) (int, error)
    // Text writes out a string as plain text.
    Text(text string) (int, error)
    // HTML writes out a string as text/html.
    HTML(htmlContents string) (int, error)
    // JSON marshals the given interface object and writes the JSON response.
    JSON(v interface{}, options ...JSON) (int, error)
    // JSONP marshals the given interface object and writes the JSON response.
    JSONP(v interface{}, options ...JSONP) (int, error)
    // XML marshals the given interface object and writes the XML response.
    XML(v interface{}, options ...XML) (int, error)
    // Markdown parses the markdown to html and renders to client.
    Markdown(markdownB []byte, options ...Markdown) (int, error)

    //  +------------------------------------------------------------+
    //  | Serve files                                                |
    //  +------------------------------------------------------------+

    // ServeContent serves content, headers are autoset
    // receives three parameters, it's low-level function, instead you can use .ServeFile(string,bool)/SendFile(string,string)
    //
    // You can define your own "Content-Type" header also, after this function call
    // Doesn't implements resuming (by range), use ctx.SendFile instead
    ServeContent(content io.ReadSeeker, filename string, modtime time.Time, gzipCompression bool) error
    // ServeFile serves a view file, to send a file ( zip for example) to the client you should use the SendFile(serverfilename,clientfilename)
    // receives two parameters
    // filename/path (string)
    // gzipCompression (bool)
    //
    // You can define your own "Content-Type" header also, after this function call
    // This function doesn't implement resuming (by range), use ctx.SendFile instead
    //
    // Use it when you want to serve css/js/... files to the client, for bigger files and 'force-download' use the SendFile.
    ServeFile(filename string, gzipCompression bool) error
    // SendFile sends file for force-download to the client
    //
    // Use this instead of ServeFile to 'force-download' bigger files to the client.
    SendFile(filename string, destinationName string) error

    //  +------------------------------------------------------------+
    //  | Cookies                                                    |
    //  +------------------------------------------------------------+

    // SetCookie adds a cookie
    SetCookie(cookie *http.Cookie)
    // SetCookieKV adds a cookie, receives just a name(string) and a value(string)
    //
    // If you use this method, it expires at 2 hours
    // use ctx.SetCookie or http.SetCookie if you want to change more fields.
    SetCookieKV(name, value string)
    // GetCookie returns cookie's value by it's name
    // returns empty string if nothing was found.
    GetCookie(name string) string
    // RemoveCookie deletes a cookie by it's name.
    RemoveCookie(name string)
    // VisitAllCookies takes a visitor which loops
    // on each (request's) cookies' name and value.
    VisitAllCookies(visitor func(name string, value string))

    // MaxAge returns the "cache-control" request header's value
    // seconds as int64
    // if header not found or parse failed then it returns -1.
    MaxAge() int64

    //  +------------------------------------------------------------+
    //  | Advanced: Response Recorder and Transactions               |
    //  +------------------------------------------------------------+

    // Record transforms the context's basic and direct responseWriter to a ResponseRecorder
    // which can be used to reset the body, reset headers, get the body,
    // get & set the status code at any time and more.
    Record()
    // Recorder returns the context's ResponseRecorder
    // if not recording then it starts recording and returns the new context's ResponseRecorder
    Recorder() *ResponseRecorder
    // IsRecording returns the response recorder and a true value
    // when the response writer is recording the status code, body, headers and so on,
    // else returns nil and false.
    IsRecording() (*ResponseRecorder, bool)

    // BeginTransaction starts a scoped transaction.
    //
    // You can search third-party articles or books on how Business Transaction works (it's quite simple, especially here).
    //
    // Note that this is unique and new
    // (=I haver never seen any other examples or code in Golang on this subject, so far, as with the most of iris features...)
    // it's not covers all paths,
    // such as databases, this should be managed by the libraries you use to make your database connection,
    // this transaction scope is only for context's response.
    // Transactions have their own middleware ecosystem also, look iris.go:UseTransaction.
    //
    // See https://github.com/kataras/iris/tree/master/_examples/ for more
    BeginTransaction(pipe func(t *Transaction))
    // SkipTransactions if called then skip the rest of the transactions
    // or all of them if called before the first transaction
    SkipTransactions()
    // TransactionsSkipped returns true if the transactions skipped or canceled at all.
    TransactionsSkipped() bool

    // Exec calls the framewrok's ServeCtx
    // based on this context but with a changed method and path
    // like it was requested by the user, but it is not.
    //
    // Offline means that the route is registered to the iris and have all features that a normal route has
    // BUT it isn't available by browsing, its handlers executed only when other handler's context call them
    // it can validate paths, has sessions, path parameters and all.
    //
    // You can find the Route by app.GetRoute("theRouteName")
    // you can set a route name as: myRoute := app.Get("/mypath", handler)("theRouteName")
    // that will set a name to the route and returns its RouteInfo instance for further usage.
    //
    // It doesn't changes the global state, if a route was "offline" it remains offline.
    //
    // app.None(...) and app.GetRoutes().Offline(route)/.Online(route, method)
    //
    // Example: https://github.com/kataras/iris/tree/master/_examples/routing/route-state
    //
    // User can get the response by simple using rec := ctx.Recorder(); rec.Body()/rec.StatusCode()/rec.Header().
    //
    // Context's Values and the Session are kept in order to be able to communicate via the result route.
    //
    // It's for extreme use cases, 99% of the times will never be useful for you.
    Exec(method string, path string)

    // Application returns the iris app instance which belongs to this context.
    // Worth to notice that this function returns an interface
    // of the Application, which contains methods that are safe
    // to be executed at serve-time. The full app's fields
    // and methods are not available here for the developer's safety.
    Application() Application
}
```