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Author:halw

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Date:2011-05-11T20:47:35.000000Z


git-svn-id: https://svn.eiffel.com/eiffel-org/trunk@889 abb3cda0-5349-4a8f-a601-0c33ac3a8c38
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halw
2011-05-11 20:47:35 +00:00
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documentation/current/solutions/concurrent-computing/concurrent-eiffel-scoop/scoop-examples/observer-pattern.wiki
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@@ -20,5 +20,12 @@ The important classes here are <code>DEGREE_5</code>, <code>EIFFEL_PARSER_POOL</
When <code>DEGREE_5</code> creates the <code>EIFFEL_PARSER_POOL</code>, it provides a maximum number of parsers to be held in the pool and a function agent which the pool can use to create a new parser instance. Then when <code>DEGREE_5</code> asks the pool to parse a file, it provides references to the file itself and two procedure agents: one for pre-parse processing and one for post-parse processing.
The pre-parse processing gives the <code>EIFFEL_PARSER_POOL</code> an agent that can be used to set up a parser before asking it to parse a file.
When an <code>EIFFEL_PARSER</code> finishes with a file, it calls the agent for post-parse processing. In this way, it notifies the instance of <code>DEGREE_5</code> that it is done with that file.
So, it is here that elements of the observer pattern are shown. In more typical observer pattern examples, there is one observed object an a set of one or more observers. But here, there is one observer, the instance of <code>DEGREE_5</code>, and many observable objects, the parsers. Also, instead of making calls directly to the observer, the observed objects apply the agents that have been provided by the observer.