Angular - using a variable as type in inheritance

Question

I have this child class :

export class ChildService extends ParentService {
  protected model = ChildModel;
}

In the parent, I would like to use the child's model as a type for the response of a http call, and for the promise !

getData(): Promise<this.model> { // doesn't work
  return this.http.get(this.url)
    .toPromise()
    .then(response => response as this.model) // doesn't work
    .catch(this.handleError);
}

Is it possible ?

Reactgular · Accepted Answer · 2018-07-17 23:11:59Z

1

Use type generics.

export class ChildService extends ParentService<ChildModel> {
}

class ParentService<TType> {
   getData(): Promise<TType> {
      return this.http.get(this.url)
     .toPromise()
         .then(response => response as TType)
         .catch(this.handleError);
   }
}

answered Jul 17, 2018 at 23:11

Reactgular

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3 Comments

Jeremy Belolo Over a year ago

That looks awesome !

Jeremy Belolo Over a year ago

What if another function in the same class needs to use another type ?

Reactgular Over a year ago

@JeremyBelolo can you give me an example? You can use more than one type for generics <TTypeA, TTypeB, TTypeC>. Methods can also have their own local types getData<DataType>: Promise<DataType> {...}

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