play/scala , implicit request => what is meaning? [duplicate] - scala

Question

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Implicit parameter for literal function
(1 answer)
Closed 6 years ago.
Most of the play framework I see the block of code
// Returns a tasks or an 'ItemNotFound' error
def info(id: Long) = SecuredApiAction { implicit request =>
maybeItem(Task.findById(id))
}
yes my understanding is define a method info(id: Long) and in scala doc to create function in scala the syntax look like this:
def functionName ([list of parameters]) : [return type] = {
function body
return [expr]
}
Can you tell me what is the meaning of implicit request => and SecuredApiAction put before {

Answer 1

play.api.mvc.Action has helper methods for processing requests and returning results. One if it's apply overloads accepts a play.api.mvc.Request parameter:
def apply(request: Request[A]): Future[Result]
By marking the request parameter as implicit, you're allowing other methods which implicitly require the parameter to use it. It also stated in the Play Framework documentation:
It is often useful to mark the request parameter as implicit so it can
be implicitly used by other APIs that need it.
It would be same if you created a method yourself and marked one if it's parameters implicit:
object X {
def m(): Unit = {
implicit val myInt = 42
y()
}
def y()(implicit i: Int): Unit = {
println(i)
}
}
Because there is an implicit in scope, when invoking y() the myInt variable will be implicitly passed to the method.
scala> :pa
// Entering paste mode (ctrl-D to finish)
object X {
def m(): Unit = {
implicit val myInt = 42
y()
}
def y()(implicit i: Int): Unit = {
println(i)
}
}
// Exiting paste mode, now interpreting.
defined object X
scala> X.m()
42