How do you implement undo and redo in Command patterns?
When doing an undo, we take the top command from the undo stack and execute its undo() what restores the “original” state. The undone command is pushed to the redoStack(). When doing a redo, we take the top command from the redo stack and execute its redo() what restores the “new” state.
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How do you implement undo and redo in Command patterns?
When doing an undo, we take the top command from the undo stack and execute its undo() what restores the “original” state. The undone command is pushed to the redoStack(). When doing a redo, we take the top command from the redo stack and execute its redo() what restores the “new” state.
Which design pattern would you likely use when you want to support undo and redo functionality?
You can use the Memento pattern for saving a copy of state and for later retrieval if necessary. The Memento pattern, like the Command pattern, is also commonly used for implementing UNDO/REDO functionality within your application.
How does undo/redo work?
When the user does an Undo, the Undo stack is popped, Undo is called on that EditAction, and the action is pushed onto the Redo stack. When the user does a Redo, the Redo stack is popped, Redo is called, and the action is pushed onto the Undo stack.
How do you implement undo and redo in C?
If “UNDO” string is encountered, pop the top element from Undo stack and push it to Redo stack. If “REDO” string is encountered, pop the top element of Redo stack and push it into the Undo stack. If “READ” string is encountered, print all the elements of the Undo stack in reverse order.
Which of the following design patterns use the stack to implement undo and redo functionality?
The memento pattern is a software design pattern that provides the ability to restore an object to its previous state (undo via rollback).
How do you undo in a text box?
By right-clicking on a TextBox, a popup menu containing an Undo entry is presented. This Undo will undo only one action, which may include several edits. An immediate subsequent Undo will undo the Undo – in essence, a Redo. The same behavior can be achieved using Ctrl + Z .
Which data structure is used to implement undo and redo?
Stack data structure
Explanation: Stack data structure is most suitable to implement redo-undo feature. This is because the stack is implemented with LIFO(last in first out) order which is equivalent to redo-undo feature i.e. the last re-do is undo first.
What is the use of Redo command?
Undo, redo, and other shortcut key functions
| Command SHORTCUT KEY | Procedure |
|---|---|
| Redo CTRL+Y | To reverse your last Undo, press CTRL+Y. You can reverse more than one action that has been undone. You can use Redo command only after Undo command. |
What is redo hotkey?
To redo something you’ve undone, press Ctrl+Y or F4.
What is the Redo Command?
In most Microsoft Windows applications, the keyboard shortcut for the undo command is Ctrl+Z or Alt+Backspace, and the shortcut for redo is Ctrl+Y or Ctrl+Shift+Z.
How do you undo and redo a stack?
So when you pop the undo stack to undo a command, you push the same command you popped into the redo stack. You do the same thing in reverse when you redo a command. You pop the redo stack and push the popped command back into the undo stack.
