Behavioral Patterns - Applied Java Patterns - page 34

A MacroCommand contains a list of subcommands. When the execute method is called, the MacroCommand
forwards subcommands.
If the MacroCommand supports undo, all internal commands must support it as well. When undo is called, this call
must be forwarded to the children in the reverse order of the execute method.
Related Patterns
Related patterns include the following:
Composite (page 157) - Use the Composite pattern to implement MacroCommands .
Memento (page 88) - Keeps the state of the receiver within the command to support undoing a Command.
Prototype (page 28) - The Prototype pattern can be used to copy the command before placing it in the history
list.
Singleton (page 34) - In most applications, the history list is implemented as a Singleton.
Example
Note:
For a full working example of this code example, with additional supporting classes and/or a RunPattern class,
see “ Command ” on page 374 of the “ Full Code Examples ” appendix.
In the Personal Information Manager, users might want to update or modify information in their system. This
code demonstrates how the Command pattern can provide update and undo behavior for a location.
In this example, a pair of interfaces model the generic command behavior. The basic command action is defined
by the execute method in Command , while UndoableCommand extends this interface by adding undo and redo
methods.
Example 2.4 Command.java
1. public interface Command{
2. public void execute();
3. }
Example 2.5 UndoableCommand.java
1. public interface UndoableCommand extends Command{
2. public void undo();