CODEWITHSUNDEEP
javascripttypescripttypestypescript-typingstypescript-generics
Tobiq
Tobiq

Reputation: 2657

How to get "this" type in typescript

class A {
    method : this = () => this;
}

What I want is for this, used as the return type, to represent the current class, i.e a subclass a of A. So, method only returns the values of the same type as the class (not only the base class, A).

I think I've got something similar with this:

class A {
    method : <T extends A> () => T = () => this;
}

But this seems superfluous. I've duplicated A. Surely there's a better way to do this?..

Upvotes: 0

Views: 1865

Answers (1)

artem
artem

Reputation: 51769

You almost got it, the type of method property should be declared as () => this, not just this. The compiler understands that when used as a type, this is polymorphic

class A {
    method : () => this = () => this;
}

class B extends A {

}

const b = new B();

const bb = b.method(); // inferred as const bb: B;

Upvotes: 1

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