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

E50060 — TraitName.methodName() must name a method the trait really declares. LeftInfo has getInfo(), not getDetails(), so the call cannot be resolved and the compiler reports E50060. EK9 has no casting, so there is no ((LeftInfo)this) form to reach it. See ek9 -h E50060 for details.

Incorrect:

        <- rtn as String: LeftInfo.getDetails()

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