override List with List

Question

I have base classes like this:

public class Scene
{
    public IList<SceneModel> Models {get; set;}
}

public class SceneModel { }

and derived classes like this:

public class WorldScene : Scene
{
    public override IList<WorldModel> Models {get; set;}
}

public class WorldModel : SceneModel { }

So my question is, how do I manage this. As it stands the compiler isn't happy with this (and to be honest it looks a bit weird to me anyway). So is what I'm trying to do impossible? And if so, why? Or is it possible and I'm just going about it the wrong way?

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score 10 · Accepted Answer · answered Oct 27 '12 at 23:42

10

You can use generics

public class BaseScene<T>
    where T : SceneModel
{
    public IList<T> Models {get; set;}
}

public class Scene : BaseScene<SceneModel>
{
}

public class WorldScene : BaseScene<WorldModel>
{    
}

Each type of scene will be parametrized by corresponding model type. Thus you will have strongly typed list of models for each scene.

answered Oct 27 '12 at 23:42

Sergey Berezovskiy

232,247
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Wow, I never knew how to do this. Thank you very much! – AxelWass Dec 10 '16 at 01:51
This is REALLY useful, this basically saved my project from having a lot of unnecessary reflection, or tons of code duplication. Thanks a lot! – Frederik Oct 05 '20 at 10:20

score 2 · Answer 2 · answered Oct 27 '12 at 23:43

2

This is fundamentally impossible.

What would happen if you write

Scene x = new WorldScene();
x.Models.Add(new OtherModel());

You just added an OtherModel to a List<WorldModel>.

Instead, you should make the base class generic.

answered Oct 27 '12 at 23:43

SLaks

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override List with List

2 Answers2

Linked