Command(Chapter 20 of Pro Objective-C Design Patterns for iOS)

You’d naturally think about using the pattern when

􀀁  You want your application to support undo/redo.

􀀁  You want to parameterize an action as an object to perform operations and replace callbacks with different command objects

􀀁  You want to specify, queue, and execute requests at different times.

􀀁  You want to log changes so they can be reapplied later in case of a system failure.

􀀁  You want the system to support transactions with which a transaction encapsulates a set of changes to data.