Re: Base class with member parameterized on type of extending class

[Jacob Carlborg via Digitalmars-d-learn]

On 2014-10-20 12:27, rcor wrote:

I would, as I need to keep track of the current scene in a variable
somewhere:
   Scene _currentScene; // problematic if Scene is a template

If the state machine doesn't need to be exposed you can create base 
class for Scene which is not templated:

abstract class Scene {} // As it is now minus the state machine

abstract class ConcreteScene (T) : Scene
{
    private StateMachine!T _stateMachine;

    // other code that need access to _stateMachine
}

class MainMenu : ConcreteScene!(MainMenu)  {}

Scene _currentScene = new MainMenu;

"ConcreteScene" might not be the best name of an abstract class.

I could just declare the StateMachine separately in every Scene, but
that seems like a lot of duplicate code (I then repeat the same code for
updating the state machine, ect.)

Or you could use a template mixin:

template StateMachineMixin (T)
{
    private StateMachine!T _stateMachine;

    // other code that need access to _stateMachine
}

class MainMenu : Scene
{
    mixin StateMachineMixin!(typeof(this));
}

--
/Jacob Carlborg