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Association vs. Dependency vs. Aggregation vs. Composition
https://nirajrules.wordpress.com/2011/07/15/association-vs-dependency-vs-aggregation-vs-composition/
An useful comment:
I always view association as something to be used in an early stage of analysis. Once a model has been created, the associations indicate potential dependencies. It then becomes an exercise in reducing dependencies to decrease coupling and increase orthogonality.The next stage would then be to determine whether an object needs a member reference to the object it depends on or if it is just transient for a particular method or methods. An exercise in managing dependency injection I guess :)If it is decided that the reference needs to be a member of the dependent object, then the dependency becomes an aggregation.Then if the dependent object needs to own the object that it depends on and control its lifetime then the aggregation becomes a composition.So I guess I see all the relationships as extension of each other. Composition extends Aggregation, Aggregation extends Dependency and Dependency extends Association.
UML Class Diagram: Association, Aggregation and Composition
http://aviadezra.blogspot.com/2009/05/uml-association-aggregation-composition.html
Dependency in UML
http://www.uml-diagrams.org/dependency.html
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原文地址：http://www.cnblogs.com/smcnblogs/p/4612897.html
