How to do it ?
+(Class)layerClass {
    return [CAEAGLLayer class] or [CAMetalLayer class];
}

Why should you do it ?

• Your view draws content using Metal or OpenGL ES, in which case you would use a CAMetalLayer or CAEAGLLayer object.
• There is a specialized layer class that offers better performance.
• You want to take advantage of some specialized Core Animation layer classes, such as particle emitters or replicators.