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34 lines
1.3 KiB
ReStructuredText
34 lines
1.3 KiB
ReStructuredText
.. BACpypes core module
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.. module:: singleton
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Singleton
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=========
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Singleton classes are a `design pattern <http://en.wikipedia.org/wiki/Singleton_pattern>`_
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which returns the same object for every 'create an instance' call. In the case
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of BACpypes there can only be one instance of a :class:`task.TaskManager` and
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all of the tasks are scheduled through it. The design pattern "hides" all
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of the implementation details of the task manager behind its interface.
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There are occasions when the task manager needs to provide additional
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functionality, or a derived class would like a change to intercept the methods.
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In this case the developer can create a subclass of :class:`TaskManager`, then
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create an instance of it. Every subsequent call to get a task manager will
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return this special instance.
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Classes
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-------
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.. class:: Singleton
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By inheriting from this class, all calls to build an object will return
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the same object.
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.. class:: SingletonLogging
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This special class binds together the metaclasses from both this singleton
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module and from the :class:`debugging.Logging`. Python classes cannot
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inherit from two separate metaclasses at the same time, but this class takes
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advantage of Pythons ability to have multiple inheritance of metaclasses.
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