When B extends A, is it possible for A to define a method that generates a new instance of B?
class SetA {
constructor(public items:any[]) {
}
createNew(items){
return new *typeof this*(items); //<-- insert actual implementation here
}
clone(){
return this.createNew(this.items);
}
}
class SetB extends SetA { }
var x = new SetB([1,2,3]);
x.clone(); //<-- creates a new SetB object
Below is the solution:
type SetConstructor<T extends SetA> = {
new (items:any[]): T;
}
class SetA {
constructor(public items:any[]) {}
createNew(items): this {
return new (this.constructor as SetConstructor<this>)(items);
}
clone(){
return this.createNew(this.items);
}
}
The createNew method has a return type of this, leveraging Polymorphic this types.
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