CODEWITHSUNDEEP
typesdart
Freewind
Freewind

Reputation: 198198

How to declare child's type in parent class?

Dart code:

main() {
    var child1 = new Child1();
    var t = child1.childType();
}

class Parent {
    ??? childType() {
        return this.runtimeType;
    }
}

class Child1 extends Parent {
}

class Child2 extends Parent {
}

You can see the ??? in class Parent, I want it to reference to child's type, but I don' know how to declare it.

In scala, it can be:

def childType(): this.type = {
    ...
}

But I don't know how to do it in dart. Is it possible? If not possible, what's the best type to use here?

Upvotes: 1

Views: 157

Answers (1)

Justin Fagnani
Justin Fagnani

Reputation: 11171

If you really need the return type of childType to statically be declared as the right subtype, you can use generics:

class Parent<C extends Parent> {
  C get childType => runtimeType;
}

class Child1 extends Parent<Child1> {}

class Child2 extends Parent<Child2> {}

I'd really make sure you need that though. You could just keep childType typed as Parent.

Upvotes: 3

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