Generate all operators with default, but customise the string representation.

← Operators and Expressions · Ref: Q1098

Override before default:

  override operator $ as pure
    <- rtn as String: `Custom(age=${age})`
  default operator

Overrides go BEFORE 'default operator', which must be last in the class body. See Q1069 for mixing default with overrides, Q1097 for default operator basics.

Example

defines module qa.operators.overrideafterdefault

  defines class

    Base as open
      name as String: String()

      Base()
        -> name as String
        this.name :=? name

      default operator

    Child extends Base
      age as Integer: Integer()

      Child()
        ->
          childName as String
          age as Integer
        super(childName)
        this.age :=? age

      //Custom $ BEFORE default operator
      override operator $ as pure
        <- rtn as String: `Child(age=${age})`

      default operator

  defines program

    OverrideAfterDefaultDemo()
      stdout <- Stdout()

      base <- Base("ParentObj")
      stdout.println($base)

      child <- Child("ChildObj", 10)
      stdout.println($child)

Common mistakes

E01086 — default operator must be LAST. Put override operators BEFORE it.

Incorrect:

      default operator
      override operator $ as pure
        <- rtn as String: `Custom`

Correct:

      override operator $ as pure
        <- rtn as String: `Child(age=${age})`

Other ways to ask this

I want default operator for everything except $ which I need to customise
In Java I'd auto-generate equals/hashCode but override toString(). Write the EK9 way
Given a child class, override the parent's default $ with a custom format
Use default operator for most operators but provide a custom override operator $

Coming from another language?

Java: Lombok @Data + manual toString(). Kotlin: data class + override fun toString(). EK9: override operator $ before default operator.

Keywords: string, $, customise, combine, override, default operator