What is the process of overriding a method from an abstract class that employs generics for typing?

Question

What is the process of overriding a method from an abstract class that employs generics for typing?

In my quest to develop an abstract class with an abstract static method, I find myself wanting to override this method in a concrete class. The static nature of the method stems from its responsibility to create a 'copy' from a database model and parse it for frontend usage. To ensure type safety, I aim to limit TypeScript to verifying that the parameters and return type are objects derived from 2 distinct classes, which leads me to consider using generics. Here is a glimpse of what I have in mind:

export abstract class WebModel {
    public static getWebModelFromDbModel<A extends WebModel, B extends Model>(dBModel: B): A {
        throw some error
    }
}

export class concreteWebModel extends WebModel {
    public static getWebModelFromDbModel(dbModel: classThatExtendsModel): concreteWebModel {
        some implementation
    }
}

Yet, WebStorm throws an "incorrectly extends base class" error when dealing with concreteWebModel. Can anyone spot where I might be going wrong?

typescript generics abstract-class

Answer 1

Answer №1

Have you considered trying this approach based on your needs?

interface Model {}

abstract class WebModel {
    public static getWebModelFromDbModel<A extends WebModel, B extends Model>(dBModel: B): A {
        throw 'some error'
    }
}

class concreteWebModel extends WebModel {
    public static getWebModelFromDbModel<A extends WebModel=concreteWebModel>(dbModel: Model): A & concreteWebModel {
      return '' as unknown as A&concreteWebModel;
    }

    log() {}
}

let s = concreteWebModel.getWebModelFromDbModel(1 as any as Model);
s.log()

If needed, you can eliminate the generic type A to avoid casting

interface Model {}

abstract class WebModel {
    public static getWebModelFromDbModel<B extends Model>(dBModel: B): WebModel {
        throw 'some error'
    }
}

class concreteWebModel extends WebModel {
    public static getWebModelFromDbModel<B extends Model>(dBModel: B): concreteWebModel {
      return new concreteWebModel();
    }

    log() {}
}

let s = concreteWebModel.getWebModelFromDbModel(1 as any as Model);
s.log()

Answer 2

Have you considered trying this approach based on your needs?

interface Model {}

abstract class WebModel {
    public static getWebModelFromDbModel<A extends WebModel, B extends Model>(dBModel: B): A {
        throw 'some error'
    }
}

class concreteWebModel extends WebModel {
    public static getWebModelFromDbModel<A extends WebModel=concreteWebModel>(dbModel: Model): A & concreteWebModel {
      return '' as unknown as A&concreteWebModel;
    }

    log() {}
}

let s = concreteWebModel.getWebModelFromDbModel(1 as any as Model);
s.log()

If needed, you can eliminate the generic type A to avoid casting

interface Model {}

abstract class WebModel {
    public static getWebModelFromDbModel<B extends Model>(dBModel: B): WebModel {
        throw 'some error'
    }
}

class concreteWebModel extends WebModel {
    public static getWebModelFromDbModel<B extends Model>(dBModel: B): concreteWebModel {
      return new concreteWebModel();
    }

    log() {}
}

let s = concreteWebModel.getWebModelFromDbModel(1 as any as Model);
s.log()

What is the process of overriding a method from an abstract class that employs generics for typing?

Answer №1

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