Question

ScalaForms

In the example linked here there is this example about form validation:

// You can also define ad-hoc constraints on the fields:
val loginForm = Form(
  tuple(
    "email" -> nonEmptyText,
    "password" -> text
  ) verifying("Invalid user name or password", fields => fields match { 
      case (e, p) => User.authenticate(e,p).isDefined 
  })
)

Via binding errors some constraints are displayed in my form. (Like the nonEmptyText, that gets a extra line behind the field stating This field is required. See:

loginForm.bindFromRequest.fold(
  formWithErrors => // binding failure, you retrieve the form containing errors,
  value => // binding success, you get the actual value 
)

If I do a .toString to the formWithErrors i get this for the nonEmptyText constraint:

Form(ObjectMapping2(<function2>,<function1>,(Email adress,FieldMapping(,List(Constraint(Some(constraint.required),WrappedArray())))),(Password,FieldMapping(,List(Constraint(Some(constraint.required),WrappedArray())))),,List(Constraint(None,List()))),Map(Password -> test, Email adress -> ),List(FormError(Email adress,error.required,WrappedArray())),None)

The latter part is a FormError List: List(FormError(Email adress,error.required,WrappedArray())),None) which is a case class: case class FormError (key: String, message: String, args: Seq[Any]) where key is defined as: The error key (should be associated with a field using the same key)..

The FieldConstructor picks this up and makes the ‘Email adress’ input box go red and add the error message (‘This field is required’).

Displaying the ad hoc constraints?

So when the form fields are all filled the username and password are checked:

verifying("Invalid user name or password", fields => fields match { 
      case (e, p) => User.authenticate(e,p).isDefined 
  })

But i dont know how to display the ‘Invalid user name or password’ to the user. The .toString of the FormError List of formWithErrors is:

List(FormError(,Invalid user name or password,WrappedArray())),None)

The Key part is empty.

Question

How do i display the ad hoc error?

I even tried:

BadRequest( views.html.test( formWithErrors ) ).flashing( "error" -> "Invalid user name or password." ) },

but for some reason its not working via the Flash either :(. This @flash.get("error").getOrElse("no 'error'") gives me ‘no error’ each time.

Answer 1

Actually, a form can have errors attached to it, so then when a bind from request fails validating constraint, a new form is created based on the given one, but filled in with errors.

Such errors list is composed of FormError which refers a Form Field and overrides toString to show its embed message.

This way if you wish to show all messages at once, you can simply formWithErrors.errors.mkString("<br>") for instance (in you template or flashing it).

There are a lot of ways and some common ones are described here http://www.playframework.org/documentation/2.0.2/ScalaFormHelpers. You might define your own field constructor as well.

To conclude, my advice would be that you should use helpers amap (for instance @inputText and ^co) because they already contain the logic to show helpers, tips and errors when available.

Edit

I missed the hint about the flash problem… you’ve probably forgotten to add (implicit flash: Flash) to you template param list. (don’t forget to flag the request as implicit as well in your action definition)