Spinning with CABasicAnimation
In this section, you are going to use an animation object to spin the implicit layer of the time field in HypnoTime’s TimeViewController whenever it is updated (Figure 23.5). (Recall that an implicit layer is a layer created by a view when the view is instantiated. The time field is a UILabel, which is a subclass of UIView, so it has an implicit layer that we can animate.)
Figure 23.5 Current time mid-spin
The Core Animation code you will write in this exercise will be in TimeViewController.m. So import the header from the QuartzCore framework at the top of this file.
#import <QuartzCore/QuartzCore.h> ...