iOS Programming: The Big Nerd Ranch Guide

For the More Curious: Pros and Cons of Callback Options

A callback, as you may remember from Chapter 4, is a chunk of code that you supply in advance of an event occurring. When that event goes down, the chunk of code gets executed. In this chapter, you have seen that blocks can be used as callbacks. Other approaches to callbacks you have seen in this book are delegation, target-action pairs, and notifications. Each one has benefits and drawbacks compared to the others. This section will expand on these benefits and drawbacks so that you can pick the appropriate one for your own implementations.

First, let’s note that each of these approaches to callbacks are design patterns that transcend their implementations in Cocoa Touch. For example, the ...