CODEWITHSUNDEEP
scala
user8215502
user8215502

Reputation: 201

Scala: it is possible to use generic type at runtime?

i wonder if i can change the implementation of such a method:

def foo() {
   val json : String = ; // get json from somewhere
   val jsonAst = new String(json).parseJson // or JsonParser(source)
   val msg = jsonAst.convertTo[UserDetails]

}

so i can provide the "UserDetails" as parameter

so calling foo will be something like:

foo[UserDetails]()....

by the way:

convertTo signature is:

def convertTo[T :JsonReader]: T = jsonReader[T].read(this)

trait JsonReader[T] {
   def read(json: JsValue): T
}

Upvotes: 1

Views: 101

Answers (2)

MAlo
MAlo

Reputation: 46

Dima's solution should be working, but your implementation of convertTo seems strange. I think it should be something like :

def convertTo[T :JsonReader]: T = implicitly[JsonReader[T]].read(this)

Upvotes: 0

Dima
Dima

Reputation: 40510

You should be able to just declare your function the same way:

def foo[T : JsonReader] = { 
  ...
  val msg = jsonAst.convertTo[T] 
}

UPDATE To elaborate, since there appears to be some confusion in the comments. def foo[T : JsonReader] does not mean that it accepts only subclasses of JsonReader. That declaration is actually equivalent to this: def foo[T](implicit jsonReader: JsonReader[T])

Upvotes: 2

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