The Core iOS Developer’s Cookbook, Fifth Edition

Delegation

Table view data sources and delegates are examples of delegation, assigning responsibility for specific activities and information to a secondary object. Several UIKit classes use delegation to respond to user interactions and to provide content. For example, when you set a table’s delegate, you tell it to pass along any interaction messages and let that delegate take responsibility for them.

Table views provide a good example of delegation. When a user taps on a table row, the UITableView instance has no built-in way of responding to that tap. The class is general purpose, and it provides no native semantics for taps. Instead, it consults its delegate—usually a view controller class—and passes along the selection change. You add ...