i18n error: controller and templates uses different implicit languages

Question

Controller:

def test = Action { implicit request =>
    import play.api.i18n._
    val msg = Messages(\"error.invalid\")
    implicit val langInController         


        

Answer 1

The play.api.i18n.Messages(key) function takes an additional implicit parameter of type Lang. So when you write Messages("foo") it is expanded to Messages("foo")(l), where l is a value of type Lang taken from the current implicit scope.

There’s always an available default implicit lang (which has a low priority), using your jvm default locale.

But when you are inside a Controller, an implicit value with a higher priority can be found if there is an implicit request. This value looks in the Accept-Language header of the request.

When you are inside a template, the default implicit lang will be used unless your template imports another implicit lang.

That’s why, in your example, messages computed from the Controller use the Accept-Language request header and messages computed from the View use your jvm default locale.

If you add an implicit parameter of type Lang to your template, this parameter will have a higher priority than the default lang and will be used to compute messages:

@(langInController: Lang, msg:String)(implicit request: RequestHeader, lang: Lang)

<div>Lang from controller: @langInController, Message: @msg</div>
<div>Message from view: @Messages("error.required")</div>

When you’ll call the template from a Controller action, its implicit lang will be passed, so the same lang will be used by both your Views and your Controllers.