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| ==Introduction==
| | 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 wiki article discusses about some of the commonly used & easy to understand Desgin patterns[http://en.wikipedia.org/wiki/Design_pattern_(computer_science)] in the software industry. Specifically, we will be studying about the Singleton, Adapter, Command & Strategy patterns. | |
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| ==Design Pattern==
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| ===Definition===
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| ===Examples===
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| ==Case Study==
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| ===Singleton===
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| [http://en.wikipedia.org/wiki/Singleton_pattern Singleton] is a design pattern which imposes a restriction on the class to instantiate exactly one object of that class.
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| ====When should we use Singleton ?==== <ref>[http://stackoverflow.com/questions/228164/on-design-patterns-when-to-use-the-singleton When should we use Singleton ?]</ref>
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| For an object to be considered as a singleton object, they must satisfy three requirements:
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| #controls concurrent access to a shared resource.
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| #access to the resource will be requested from multiple, disparate parts of the system.
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| #there can be only one object.
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| ====Uses====
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| ====Advantages====
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| *Singletons are often preferred to global variables as they don't pollute the global [http://en.wikipedia.org/wiki/Namespace namespace] with unnecessary variables & also can be instantiated only when needed unlike global variables which always consume resources.
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| ====Drawbacks====
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| *Introduces a global state into the application.
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| *Can make unit testing classes in isolation difficult.
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| ===Adapter===
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| ===Command===
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| ===Strategy===
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| ==Conclusion==
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| ==References==
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| <references/>
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| ==External Links==
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Latest revision as of 04:54, 21 October 2011