CSC/ECE 517 Fall 2012/ch2b 2w40 sn

Introduction to Command Pattern

The command pattern is one of the most used behavioral design patterns. The main concept of the pattern is an object which can be used to represent and encapsulate all the information needed to call a method at a later time. This information includes the method name, the object that owns the method and values for the method parameters.

The command pattern has been often associated with these terms client, invoker and receiver. The client instantiates the command object and provides the information required to call the method at a later time. The invoker decides when the method should be called. The receiver is an instance of the class that contains the method's code.

Using command objects makes it easier to construct general components that need to delegate, sequence or execute method calls at a time of their choosing without the need to know the owner of the method or the method parameters.