[Note] Collaborator vs. the Factory

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Collaborator vs. the Factory

• your code should either be in the business of doing business logic or in the business of instantiating and wiring other objects together

• What this effectively means is that your either have classes with ifs and loops (your business logic) or you have classes with new operators (your factories).要么处理逻辑,要么创建对象

• But in practice you only need one factory class each time you cross an object lifetime

• To allow the removal of the new operators from our business logic classes, we need to ask for our collaborators instead of making them
•  This means that each class only knows about other classes with which it is in direct contact and which it needs to get its job done.
•  The trick lies that the view of the world from the factory is different than the view from the collaborator.
• The collaborators only know about its direct dependecies and the factories know about everything, and that is a good thing. 

But in my experience I saw there are times when objects are created based on business logic. So, some object requires a certain object, with a certain interface. The tricky part is that the concrete object  type is determined at runtime in some business logic code.

•  Let the factory control the wiring process keeping the ifs out of it (as much as possible).
• A single factory can be responsible for a whole object graph, so there is not necessarily a one-to-one correspondence there between classes and factories

原文链接:Collaborator vs. the Factory