Can't get a component derived from a base class with generics defined as an interface in Unity-CodePudding

I am trying to understand why I cannot get a component on a gameobject that derives from a base class that has a generic tied to an interface.

I have the following setup for my class:

MyClass : Node<IMyInterface>

with

abstract Node<T> : Monobehaviour where T : IMyInterface

Then in a separate component on the same gameobject as MyClass i have:

GetComponent<Node<IMyInterface>>()

This always returns null when i have MyClass attached to the same GameObject. I also cannot drag the component to a public field of type Node<IMyInterface> either even though it seems to suggest I can because when I drag it over the field it highlights it as if I am able to set it there.

Why does it not allow this ? I don't see anything wrong here as the types match perfectly fine...

CodePudding user response：

I notice the interface, so I suspect you didn't declare MyClass as such, but in the following form:

class MyImpl : IMyInterface;
class MyClass : Node<MyImpl>;

Now everything makes sense.

Although Node<MyImpl> is similar to Node<IMyInterface>, they are actually different types, the assignment Node<IMyInterface> node = new MyClass(); is invalid, so GetComponent<Node<IMyInterface>>() cannot find a component which type is Node<MyImpl>.

In the inspector, both Node<MyImpl> and Node<IMyInterface> fields are shown as Node`1, it's the generic type defination (Node<>) of these classes, when you drag a Node<MyImpl> component to a Node<IMyInterface> field, only the defination is compared, that's why you can see the field highlights but cannot be set.

CodePudding user response：

MyClass : Node<IMyInterface>
abstract Node<T> : Monobehaviour where T : IMyInterface
PreciseClass : Monobehaviour , IMyInterface

GetComponent<MyClass >()//work
GetComponent<Node<PreciseClass>()//not work
GetComponent<PreciseClass>()//work

for example like this.