Collection Patterns

Abstract

Organizing collections of objects is a fundamental part of everyday programming. The class frameworks provide several classes for organizing objects into arrays, dictionaries (maps), and sets. Objects in an array have a specific order, addressed by a numeric index. Dictionaries (maps) organize objects into unordered pairs, each pair being a unique key object and a value object. The key object is used to identify and address the value object. Finally, sets are amorphous collections that are neither ordered nor addressable; an object is simply in a set or it’s not. The Cocoa framework doesn’t provide any tree, linked list, or stack collections.