Difference between revisions of "Plug-in pattern"
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:The ''plug-in'' (sometimes called the client), which is plugged into the ''host''. | :The ''plug-in'' (sometimes called the client), which is plugged into the ''host''. | ||
;Host | ;Host | ||
:The ''host'' of | :The ''host'' of the ''plug-in''. | ||
;Site | ;Site | ||
:The ''plug-in'' explose data and functionality to the ''host'', but the ''plug-in'' may also need to draw upon data and services from the ''host''. The ''site'' represent the ''plug-in'''s ''host'' access. | :The ''plug-in'' explose data and functionality to the ''host'', but the ''plug-in'' may also need to draw upon data and services from the ''host''. The ''site'' represent the ''plug-in'''s ''host'' access. | ||
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*The site interface, which defines the ''plug-in'''s view of the ''host'' | *The site interface, which defines the ''plug-in'''s view of the ''host'' | ||
Example | ;Example | ||
A SAPI (i.e. Speech API) speech recognizer engine is a plug-in hosted by the Windows SAPI system. | A SAPI (i.e. Speech API) speech recognizer engine is a plug-in hosted by the Windows SAPI system. | ||
Revision as of 11:57, 22 August 2013
The plug-in pattern is a design pattern. I believe it is widely used, but I have not seen it described anywhere, and plug-in pattern is the name I have given it.
The pattern have three actors:
- Plug-in
- The plug-in (sometimes called the client), which is plugged into the host.
- Host
- The host of the plug-in.
- Site
- The plug-in explose data and functionality to the host, but the plug-in may also need to draw upon data and services from the host. The site represent the plug-in's host access.
There are two contracts in the pattern:
- The plug-in interface, which defines the hosts view of the plug-in
- The site interface, which defines the plug-in's view of the host
- Example
A SAPI (i.e. Speech API) speech recognizer engine is a plug-in hosted by the Windows SAPI system.
The engine is the plug-in and Windows SAPI is the host. The plug-in must implement the interface ISpSREngine, which is the host's view of the engine.
The host will call the function ISpSREngine::SetSite with an object of type ISpSREngineSite. This object is the site object and gives the plug-in access to data and functionality in the host.
In the recognition process the host will feed audio buffers; notify grammar loads and unloads; etc through the ISpSREngine interface. On the other hand, the plug-in will return recognition results; interrogate about grammar details; etc. through the site (ISpSREngineSite) object.