CSC/ECE 517 Fall 2011/ch4 4h as: Difference between revisions
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==Singleton Pattern== | ==Singleton Pattern== | ||
In software engineering the singleton pattern is a creational pattern which is used to ensure that not more than one object is ever created for a class. The singleton also provides a point of global access. There may be various reasons that necessitate such a requirement for a class. | |||
===Common Applications=== | |||
The class may represent the global state of the system or the class may correspond to a master logger which writes into the log file. Some other places where the singleton pattern is applicable are device drivers, registry settings, etc. | |||
===Implementation=== | |||
There are many ways of implementing the singleton pattern. The most common way is to have a method which creates an instance of the object if it does not already exist. Otherwise the existing reference is returned. To make sure that multiple instances are not created the constructor is made private. Also the object which stores the single instance is made a class variable and is thus not tied to any particular instance of the class. | |||
==Adapter Pattern== | ==Adapter Pattern== | ||
==Command Pattern== | ==Command Pattern== | ||
Revision as of 02:03, 21 October 2011
Introduction
Software Design Patterns
Singleton Pattern
In software engineering the singleton pattern is a creational pattern which is used to ensure that not more than one object is ever created for a class. The singleton also provides a point of global access. There may be various reasons that necessitate such a requirement for a class.
Common Applications
The class may represent the global state of the system or the class may correspond to a master logger which writes into the log file. Some other places where the singleton pattern is applicable are device drivers, registry settings, etc.
Implementation
There are many ways of implementing the singleton pattern. The most common way is to have a method which creates an instance of the object if it does not already exist. Otherwise the existing reference is returned. To make sure that multiple instances are not created the constructor is made private. Also the object which stores the single instance is made a class variable and is thus not tied to any particular instance of the class.