Behavioral Design Patterns in C++ - Undo - I

The video tutorial explains the concept of command patterns, focusing on their application in transactions and the ability to compose commands into macros or queues. It discusses implementing undo and redo functionalities by storing state, which can vary based on application needs. For single-level undo, only the last command is stored, while multiple levels require a history list. The tutorial highlights the importance of storing command copies to prevent state changes from affecting previous commands. Finally, it introduces the idea of using prototypes for command objects and the need for receivers to provide operations for state restoration.

What is a key feature of commands as objects in applications?

• They can only be executed once.

• They cannot be composed together.

• They can be organized into queues.

• They do not support transactions.

Which of the following is NOT a method to store state for undo operations?

• Ignoring the state changes.

• Using the receiver object itself.

• Using the original values in the receiver.

• Storing the arguments passed to the receiver.

What does an application need to store for multiple levels of undo and redo?

• The initial state of the application.

• The final state of the application.

• Only the last executed command.

• The history of commands in a list.

Why is it important to store copies of commands in a list for undo operations?

• To simplify the command execution process.

• To reduce memory usage.

• To prevent state changes from affecting previous commands.

• To ensure commands can be executed multiple times.

What role do commands play when they act as prototypes?

• They simplify the command execution process.

• They allow for the creation of new command instances.

• They reduce the need for state storage.

• They limit the number of undo operations.