CODEWITHSUNDEEP
scalainitializationtraitscake-pattern
Adrian
Adrian

Reputation: 3792

Initializing a trait attribute while using the cake patern

Is it possible to initialize an attribute in an enclosed trait of a cake pattern? Something similar to early initializers. For example:

object CakePatternInit {

  trait A {
    var prop: String = null
  }

  trait A1 extends A

  trait B {
    this: A =>
    println(prop.toUpperCase) // I'd like here prop to be initialized already with "abc"
  }

  def main(args: Array[String]) {

    val b = new B with A1
    //  how do I initialize prop here?
    //  can I write something like this:
    //  val b = new B with { prop = "abc" } A1
  }
}

Upvotes: 0

Views: 52

Answers (1)

chengpohi
chengpohi

Reputation: 14227

  trait A {
    def prop: String
  }

  trait A1 extends A

  trait B {
    this: A =>
    println(prop.toUpperCase) // I'd like here prop to be initialized already with "abc"
  }

  val t = new B with A1 { def prop = "Hello"}
  > HELLO
  > t.prop
  res22: String = Hello

Declare your prop as method, because scala can't override var's

There is an article that can help you: cake pattern

Upvotes: 1

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