New: i18n pluralization and variables support and more...

fixes: #1649, #1648, #1641, #1650

relative to: #1597

_examples/i18n/basic/main.go

@@ -0,0 +1,125 @@
+package main
+
+import (
+	"fmt"
+	"html/template"
+
+	"github.com/kataras/iris/v12"
+)
+
+/*
+	See i18n-template for a more advanced translation key-values.
+*/
+
+func newApp() *iris.Application {
+	app := iris.New()
+
+	// Configure i18n.
+	//
+	// app.I18n.Subdomain = false to disable resolve lang code from subdomain.
+	// app.I18n.LoadAssets for go-bindata.
+
+	// Default values:
+	// app.I18n.URLParameter = "lang"
+	// app.I18n.Subdomain = true
+	//
+	// Set to false to disallow path (local) redirects,
+	// see https://github.com/kataras/iris/issues/1369.
+	// app.I18n.PathRedirect = true
+	//
+	// See `app.I18n.ExtractFunc = func(ctx iris.Context) string` or
+	// `ctx.SetLanguage(langCode string)` to change the extracted language from a request.
+	//
+	// Use DefaultMessageFunc to customize the return value of a not found key or lang.
+	// All language inputs fallback to the default locale if not matched.
+	// This is why this one accepts both input and matched languages,
+	// so the caller can be more expressful knowing those.
+	// Defaults to nil.
+	app.I18n.DefaultMessageFunc = func(langInput, langMatched, key string, args ...interface{}) string {
+		msg := fmt.Sprintf("user language input: %s: matched as: %s: not found key: %s: args: %v", langInput, langMatched, key, args)
+		app.Logger().Warn(msg)
+		return msg
+	}
+	// Load i18n when customizations are set in place.
+	//
+	// First parameter: Glob filpath patern,
+	// Second variadic parameter: Optional language tags, the first one is the default/fallback one.
+	err := app.I18n.Load("./locales/*/*.ini", "en-US", "el-GR", "zh-CN")
+	if err != nil {
+		panic(err)
+	}
+
+	app.Get("/not-matched", func(ctx iris.Context) {
+		text := ctx.Tr("not_found_key", "some", "values", 42)
+		ctx.WriteString(text)
+		// user language input: en-gb: matched as: en-US: not found key: not_found_key: args: [some values 42]
+	})
+
+	app.Get("/", func(ctx iris.Context) {
+		hi := ctx.Tr("hi", "iris")
+		locale := ctx.GetLocale()
+
+		ctx.Writef("From the language %s translated output: %s", locale.Language(), hi)
+	})
+
+	app.Get("/some-path", func(ctx iris.Context) {
+		ctx.Writef("%s", ctx.Tr("hi", "iris"))
+	})
+
+	app.Get("/other", func(ctx iris.Context) {
+		language := ctx.GetLocale().Language()
+
+		fromFirstFileValue := ctx.Tr("key1")
+		fromSecondFileValue := ctx.Tr("key2")
+		ctx.Writef("From the language: %s, translated output:\n%s=%s\n%s=%s",
+			language, "key1", fromFirstFileValue,
+			"key2", fromSecondFileValue)
+	})
+
+	// using in inside your views:
+	view := iris.HTML("./views", ".html")
+	app.RegisterView(view)
+
+	app.Get("/templates", func(ctx iris.Context) {
+		ctx.View("index.html", iris.Map{
+			"tr": ctx.Tr, // word, arguments... {call .tr "hi" "iris"}}
+			"trUnsafe": func(message string, args ...interface{}) template.HTML {
+				return template.HTML(ctx.Tr(message, args...))
+			},
+		})
+
+		// Note that,
+		// Iris automatically adds a "tr" global template function as well,
+		// the only difference is the way you call it inside your templates and
+		// that it accepts a language code as its first argument: {{ tr "el-GR" "hi" "iris"}}
+	})
+	//
+
+	return app
+}
+
+func main() {
+	app := newApp()
+
+	// go to http://localhost:8080/el-gr/some-path
+	// ^ (by path prefix)
+	//
+	// or http://el.mydomain.com8080/some-path
+	// ^ (by subdomain - test locally with the hosts file)
+	//
+	// or http://localhost:8080/zh-CN/templates
+	// ^ (by path prefix with uppercase)
+	//
+	// or http://localhost:8080/some-path?lang=el-GR
+	// ^ (by url parameter)
+	//
+	// or http://localhost:8080 (default is en-US)
+	// or http://localhost:8080/?lang=zh-CN
+	//
+	// go to http://localhost:8080/other?lang=el-GR
+	// or http://localhost:8080/other (default is en-US)
+	// or http://localhost:8080/other?lang=en-US
+	//
+	// or use cookies to set the language.
+	app.Listen(":8080", iris.WithSitemap("http://localhost:8080"))
+}