Need help understanding how strategy patterns work

[eldan88]

Hey guys. I have been trying to comprehend  how strategy patterns work.

From what I understand, they are a family of algorithms that are encapsulated in an object. (sounds self-explanatory)

But what I don't get, is what they mean by making the objects interchangeable?

 

I have been doing a lot of googling but can't find a good easy to understand example.

Does anyone have any references or examples, that you can show me?

 

Thanks a lot!!!!

[ignace]

By interchangeable they mean you can swap one for the other, as in setStrategy($strategy), now the object who has that method has his strategy changed, for example if you have a class that displays the filesystem in an hierarchy, a strategy could be to sort it by name (class SortByNameStrategy) or sorted by folders-first (class SortByFolderFirstStrategy).

 

You can change the display by changing the strategy on the filesystem object. Adapter and Strategy are quite alike from a design POV where one is about making one thing work with another, the other is about selecting the proper algorithm/behaviour.

Edited October 1, 2013 by ignace

[eldan88]

Thanks for the explanation ignace. I re-read your explanation and did some further reading and finally understood how it works. It was that AHA! moment.