Question

I was wondering if there is a way to pass in a type which is enforced to be of a certain base type. For instance, for my game engine I have a attribute list (controllable, rigidBody, etc). I have a addAttribute parameter which takes a new object. However, I would like to also have an overload which takes a type instead from which I can create a new object on my own. So for instance

public void addAttribut(Type attribute)

I am thinking of maybe something that implements linq? I have tried but it looks like “where” can be only used on generics:

public void addAttribute(Type attribute) where attribute : Attribute

would be the signature of the function. I believe that Unity does this; however it could be that it can do this through Mono.

I could always throw an exception if it is not of the correct base type. However I was wondering if there is a way to prevent the programmer from passing in the wrong time all together.

Any ideas? Any help is greatly appreciated!

Answer 1

If you’re happy for calling code to need to know the type at compile-time, you could make it a generic method with a type parameter:

public void AddAttribute<T>() where T : Attribute
{
    // Use typeof(T)
}

Or to enforce a parameterless constructor which you can then call:

public void AddAttribute<T>() where T : Attribute, new()
{
    T t = new T();
    ...
}

But otherwise there’s no way of doing it, no – you’d have to validate the argument at execution time, just like any other.