Call a C++ base class method automatically

Question

I\'m trying to implement the command design pattern, but I\'m stumbling accross a conceptual problem. Let\'s say you have a base class and a few subclasses like in the examp

Answer 1

Assuming it's a 'normal' application with undo and redo, I wouldn't try and mix managing the stack with the actions performed by the elements on the stack. It will get very complicated if you either have multiple undo chains (e.g. more than one tab open), or when you do-undo-redo, where the command has to know whether to add itself to undo or move itself from redo to undo, or move itself from undo to redo. It also means you need to mock the undo/redo stack to test the commands.

If you do want to mix them, then you will have three template methods, each taking the two stacks (or the command object needs to have references to the stacks it operates on when created), and each performing the move or add, then calling the function. But if you do have those three methods, you will see that they don't actually do anything other than call public functions on the command and are not used by any other part of the command, so become candidates the next time you refactor your code for cohesion.

Instead, I'd create an UndoRedoStack class which has an execute_command(Command*command) function, and leave the command as simple as possible.