Head First: Design Patterns by unknow

Author:unknow
Language: eng
Format: epub, pdf
Tags: COMPUTERS / Software Development & Engineering / General
ISBN: 9780596556563
Publisher: O'Reilly Media
Published: 2004-10-25T04:00:00+00:00

Let’s think about this in terms of our menus: this pattern gives us a way to create a tree structure that can handle a nested group of menus and menu items in the same structure. By putting menus and items in the same structure we create a part-whole hierarchy; that is, a tree of objects that is made of parts (menus and menu items) but that can be treated as a whole, like one big über menu.

Once we have our über menu, we can use this pattern to treat “individual objects and compositions uniformly.” What does that mean? It means if we have a tree structure of menus, submenus, and perhaps subsubmenus along with menu items, then any menu is a “composition” because it can contain both other menus and menu items. The individual objects are just the menu items — they don’t hold other objects. As you’ll see, using a design that follows the Composite Pattern is going to allow us to write some simple code that can apply the same operation (like printing!) over the entire menu structure.

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