The Core iOS Developer’s Cookbook, Fifth Edition

Touches

Cocoa Touch implements direct manipulation in the simplest way possible. It sends touch events to the view you’re interacting with. As an iOS developer, you tell the view how to respond. Before jumping into gestures and gesture recognizers, you should gain a solid foundation in this underlying touch technology. It provides the essential components of all touch-based interaction.

Each touch conveys information: where the touch took place (both the current and previous location), what phase of the touch was used (essentially mouse down, mouse moved, mouse up in the desktop application world, corresponding to finger or touch down, moved, and up in the direct manipulation world), a tap count (for example, single-tap/double-tap), and when ...