Call a specific trait's method implementation using TraitName.method() syntax.

← Sealed Types and Traits · Ref: Q1132

Call a specific trait's implementation by name:

  getLeftInfo() as pure
    <- rtn as String: LeftInfo.getInfo()
  getRightInfo() as pure
    <- rtn as String: RightInfo.getInfo()

TraitName.methodName() bypasses override resolution and goes directly to the specified trait.

See Q1131 for diamond resolution. See Q1129 for basic delegation.

Example

defines module qa.sealedtraits.traitexplicitcall

  defines trait

    LeftInfo
      getInfo() as pure
        <- rtn as String: "left-info"

    RightInfo
      getInfo() as pure
        <- rtn as String: "right-info"

  defines class

    Combined with trait of LeftInfo, RightInfo

      //Must override the conflicting method
      override getInfo() as pure
        <- rtn as String: "combined"

      //Explicit calls to each trait's version
      getFromLeft() as pure
        <- rtn as String: LeftInfo.getInfo()

      getFromRight() as pure
        <- rtn as String: RightInfo.getInfo()

      default operator ?

  defines program

    TraitExplicitCallDemo()
      stdout <- Stdout()

      combined <- Combined()
      stdout.println(`Default: ${combined.getInfo()}`)
      stdout.println(`Left: ${combined.getFromLeft()}`)
      stdout.println(`Right: ${combined.getFromRight()}`)

Common mistakes

E01010 — EK9 has no casting. Use TraitName.methodName() to call a specific trait's implementation directly.

Incorrect:

        <- rtn as String: ((LeftInfo)this).getInfo()

Correct:

        <- rtn as String: LeftInfo.getInfo()

Other ways to ask this

I need to access a particular trait's version of a method in a class with multiple traits
In Java I'd use InterfaceName.super.method(). Write the EK9 explicit trait call
Given a class with two traits providing getInfo(), call each trait's version explicitly
Disambiguate trait method calls using the TraitName.methodName() syntax

Coming from another language?

Java: InterfaceName.super.method(). C#: ((IInterface)this).Method(). EK9: TraitName.method() — direct, no casting needed.

Keywords: TraitName, explicit, specific, trait, disambiguate, call