Play framework asynchronous results - scala

Question

I changed one function from:
def submit = Action { request =>
signupForm.bindFromRequest()(request).fold(
// Form has errors
errors => BadRequest(html.signup.form(errors)),
// We got a valid User value, display the summary
user => {
// intensive computation involving database
Ok("okay")
}
)
}
to
def submit = Action { request =>
val result = Akka.future {
signupForm.bindFromRequest()(request).fold(
// Form has errors
errors => BadRequest(html.signup.form(errors)),
// We got a valid User value, display the summary
user => {
// intensive computation involving database
Ok("okay")
}
)
}
Async {
result
}
}
and I get the compilation error of:
[error] found : play.api.mvc.SimpleResult[_ >: java.lang.String with play.api.templates.Html <: java.io.Serializable]
[error] required: play.api.mvc.SimpleResult[_1(in value result)] where type _1(in value result) >: java.lang.String with play.api.templates.Html <: java.io.Serializable
[error] Note: java.io.Serializable >: _1, but class SimpleResult is invariant in type A.
[error] You may wish to define A as -A instead. (SLS 4.5)
[error] signupForm.bindFromRequest()(request).fold(
[error] ^
[error] one error found
The error message seem like it has something to do with variance. Does anyone understand what's going on?

Answer 1

BadRequest is returning the type SimpleResult[Html]
Ok is returning the type SimpleResult[String]
If you make BadRequest and Ok return the same type then it would work.
Try doing Ok(Html("ok")) - or actually render a page.