Scala Play 2.5 Form bindFromRequest：在这里找不到任何 HTTP 请求？

Question

我有一个这样实现的控制器操作：

def doChangePassword = deadbolt.Restrict(List(Array(Application.USER_ROLE_KEY)))() 
{ request => // <<<<<<<<<<<< here is the request 
  Future {
    val context = JavaHelpers.createJavaContext(request)
    com.feth.play.module.pa.controllers.AuthenticateBase.noCache(context.response())

    val filledForm = Account.PasswordChangeForm.bindFromRequest
    // compilation error here, it can't see the request ^^^^^^^

    if (filledForm.hasErrors) {
      // User did not select whether to link or not link
      BadRequest(views.html.account.password_change(userService, filledForm))
    } else {
      val Some(user: UserRow) = userService.getUser(context.session)
      val newPassword = filledForm.get.password
      userService.changePassword(user, new MyUsernamePasswordAuthUser(newPassword), true)
      Redirect(routes.Application.profile).flashing(
        Application.FLASH_MESSAGE_KEY -> messagesApi.preferred(request)("playauthenticate.change_password.success")
      )
    }
  }
}

上面的实现导致编译错误：

[error] /home/bravegag/code/play-authenticate-usage-scala/app/controllers/Account.scala:74: Cannot find any HTTP Request here
[error]         val filledForm =  Account.PasswordChangeForm.bindFromRequest
[error]                                                     ^
[error] one error found

但是，如果我将第 2 行从：

{ request => // <<<<<<<<<<<< here is the request

到

{ implicit request => // <<<<<<<<<<<< here is the request

然后编译...但是为什么？

Answer 1

你需要一个 implicit request 范围，像这样：https://github.com/pedrorijo91/play-slick3-steps/blob/master/app/controllers/ApplicationController.scala#L11

Answer 2

您要找的是Implicit Parameters。简而言之：

隐式参数可以像常规或显式参数一样传递。如果您没有显式提供隐式参数，那么编译器将尝试为您传递一个。隐式可以来自不同的地方。来自常见问题 Where does Scala look for implicits?:

First look in current scope

Implicits defined in current scope

Explicit imports

wildcard imports

Now look at associated types in

Companion objects of a type

Implicit scope of an argument’s type (2.9.1)

Implicit scope of type arguments (2.8.0)

Outer objects for nested types

Other dimensions

第 1 项下的隐含项优先于第 2 项下的隐含项。

通过在您的示例中将 request 标记为 implicit，您声明了一个 "Implicit defined in current scope"。你需要有一个隐含的请求，因为 bindFormRequest "asks" 你要通过一个。查看其签名：

bindFromRequest()(implicit request: Request[_]): Form[T]

现在你在范围内有一个 implicit request，编译器会自动将它传递给 bindFormRequerst。

正如我在开头提到的，您也可以显式传递 request：

val filledForm = Account.PasswordChangeForm.bindFromRequest()(request)

在后一种情况下，无需将 request 声明为 implicit，因为您显然明确地传递了 request。两种变体是相同的。看你喜欢哪一个。

Scala Play 2.5 Form bindFromRequest：在这里找不到任何 HTTP 请求？

Scala Play 2.5 Form bindFromRequest: Cannot find any HTTP Request here?

scala

playframework

deadbolt-2