README: add 'run in the browser' button

after the quick start details, so it is visible always


Former-commit-id: 0c13135a01c2b883aa4a9629a507aaf622d22ade

_examples/dependency-injection/context-register-dependency/main.go

@@ -0,0 +1,95 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	app := iris.New()
+	app.Use(RoleMiddleware)
+
+	app.Get("/", commonHandler)
+	c := app.ConfigureContainer()
+	/*
+		When you do NOT have access to the middleware code itself
+		then you can register a request dependency
+		which retrieves the value from the Context
+		and returns it, so handler/function's input arguments
+		with that `Role` type can be binded.
+
+		c.RegisterDependency(func(ctx iris.Context) Role {
+			role, ok := GetRole(ctx)
+			if !ok {
+				// This codeblock will never be executed here
+				// but you can stop executing a handler which depends on
+				// that dependency with `ctx.StopExecution/ctx.StopWithXXX` methods
+				// or by returning a second output argument of `error` type.
+				ctx.StopExecution()
+				return Role{}
+			}
+
+			return role
+		})
+	*/
+	c.Get("/dep", handlerWithDependencies)
+
+	// http://localhost:8080?name=kataras
+	// http://localhost:8080/dep?name=kataras
+	app.Listen(":8080")
+}
+
+func commonHandler(ctx iris.Context) {
+	role, _ := GetRole(ctx)
+	ctx.WriteString(role.Name)
+}
+
+func handlerWithDependencies(role Role) string {
+	return role.Name
+}
+
+// Code for an example middleware.
+
+// Role struct value example.
+type Role struct {
+	Name string
+}
+
+const roleContextKey = "myapp.role"
+
+// RoleMiddleware example of a custom middleware.
+func RoleMiddleware(ctx iris.Context) {
+	// [do it yourself: extract the role from the request...]
+	if ctx.URLParam("name") != "kataras" {
+		ctx.StopWithStatus(iris.StatusUnauthorized)
+		return
+	}
+	//
+
+	role := Role{Name: "admin"}
+
+	ctx.Values().Set(roleContextKey, role)
+
+	// When you have access to the middleware itself:
+	// Use the `RegisterDependency` to register
+	// struct type values as dependencies at request-time for
+	// any potential dependency injection-ed user handler.
+	// This way the user of your middleware can get rid of
+	// manually register a dependency for that `Role` type with calls of
+	// `APIContainer.RegisterDependency` (and `mvc.Application.Register`).
+	ctx.RegisterDependency(role)
+
+	ctx.Next()
+}
+
+// GetRole returns the role inside the context values,
+// the `roleMiddleware` should be executed first.
+func GetRole(ctx iris.Context) (Role, bool) {
+	v := ctx.Values().Get(roleContextKey)
+	if v != nil {
+		if role, ok := v.(Role); ok {
+			return role, true
+		}
+	}
+
+	return Role{}, false
+}
+
+// End Code of our example middleware.