CODEWITHSUNDEEP
c#abstractreturn-typebase-class
Ams1
Ams1

Reputation: 135

Abstract class method with different return type in derived class

I have this abstract class:

 abstract class Animal {

    public abstract List<??????> getAnimals();

 }

I want to change the return type to make this:

     Animal animal;

     if(/*Somthing*/){
          animal = new Cat();
          catList = animal.getAnimals();
     }else{
          animal = new Dog(); 
          dogList = animal.getAnimals();
     }

I want to return CatModelList and a DogModelList.

Is this possible if dog and cat would have Animals as base? And if not what I think is the answer, what would be the correct way of doing this?

Upvotes: 1

Views: 2012

Answers (1)

Patrick Hofman
Patrick Hofman

Reputation: 156978

Then you need generics to supply the type:

abstract class Animal<T> : Animal where T : Animal
{
    public abstract List<T> GetAnimals();
}

abstract class Animal
// base type to make things easier. Put in all the non-generic properties.
{ }

Where T could be Dog, Cat or any other type deriving from Animal:

class Dog : Animal<Dog>
{ }

Then you can use it using the derived class:

Dog d = new Dog();
animal = d;
dogList = d.GetAnimals();

It seems weird though. In an instance of Animal you get the animals? I don't get that logic.

Upvotes: 5

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