Specialized Layers - iOS Core Animation - page 114

So, let's try it using a CATransformLayer instead. The first problem to address is that
we constructed our cube in Chapter 5 using views rather than standalone layers. We cannot
place a view-backing layer inside another layer that is not itself a view-backing layer
without messing up the view hierarchy. We could create a new UIView subclass backed
by a CATransformLayer (using the + layerClass method), but to keep things simple
for our example, let's just re-create the cube using standalone layers instead of views. This
means we can't display buttons and labels on our cube faces like we did in Chapter 5, but
we don't need to do that right now.
Listing 6.5 contains the code. We position each cube face using the same basic logic we
used in Chapter 5. But instead of adding the cube faces directly to the container view's
backing layer as we did before, we place them inside a CATransformLayer to create a
standalone cube object, and then place two such cubes into our container. We've colored
the cube faces randomly so as to make it easier to distinguish them without labels or
lighting. Figure 6.5 shows the result.
Listing 6.5 Assembling a 3D Layer Hierarchy Using CATransformLayer
@interface ViewController ()
@property ( nonatomic , weak ) IBOutlet UIView *containerView;
@end
@implementation ViewController
- ( CALayer *)faceWithTransform:( CATransform3D )transform
{
//create cube face layer
CALayer *face = [ CALayer layer ];
face. frame = CGRectMake (- 50 , - 50 , 100 , 100 );
//apply a random color
CGFloat red = ( rand () / ( double ) INT_MAX );
CGFloat green = ( rand () / ( double ) INT_MAX );
CGFloat blue = ( rand () / ( double ) INT_MAX );
face. backgroundColor = [ UIColor colorWithRed :red
green :green
blue :blue
alpha : 1.0 ]. CGColor ;
//apply the transform and return
face. transform = transform;
return face;
}