|
|
| Line 1: |
Line 1: |
| This page has been moved to [http://expertiza.csc.ncsu.edu/wiki/index.php/CSC/ECE_517_Fall_2011/ch4_4h_kp http://expertiza.csc.ncsu.edu/wiki/index.php/CSC/ECE_517_Fall_2011/ch4_4h_kp] | | This page has been moved to [http://expertiza.csc.ncsu.edu/wiki/index.php/CSC/ECE_517_Fall_2011/ch4_4h_kp http://expertiza.csc.ncsu.edu/wiki/index.php/CSC/ECE_517_Fall_2011/ch4_4h_kp] |
|
| |
| ==Design Patterns at a Glance==
| |
|
| |
| {| class="wikitable" border="1"
| |
|
| |
| |-
| |
| ! Design Patterns
| |
| ! Singleton
| |
| ! Adapter
| |
| ! Command
| |
| ! Strategy
| |
|
| |
| |-
| |
| ! Purpose
| |
| | To ensure a class has only one instance, and also to provide a global point of access to it
| |
| | To convert the interface of a class into another interface the clients expects
| |
| | To encapsulate method invocations so as to decouple caller from the implementation details
| |
| | To perform a bunch of different things to do, based on the situation/context
| |
|
| |
| |-
| |
| ! Advantages
| |
| | Sane usage of global namespace by avoiding unnecessary global variables and providing on-demand (lazy) instantiations.
| |
| | It lets classes work together that could not otherwise because of incompatible interfaces.
| |
| | It allows one to decouple the requester of an action from the object that actually performs the action.
| |
| | It lets the algorithms vary independently from clients that use those.
| |
|
| |
| |-
| |
| ! Disadvantages
| |
| | Introduces global state into system and complicates unit testing.
| |
| | Adapter has to implement the entire target interface. Selective functionality implementation is not an option.
| |
| | Having Command objects specific to each action ends up cluttering the design, especially in the context of MVC architectures <ref>[http://www.codeproject.com/KB/architecture/commandpatterndemo.aspx]</ref>
| |
| | Increases the number of objects and all algorithms use the same interface. <ref> [www.cs.toronto.edu/~arnold/407/.../stateStrategy/state_strat_pres.ppt] </ref>
| |
|
| |
| |}
| |