Overview

CABasicAnimation provides basic, single-keyframe animation capabilities for a layer property. You create an instance of CABasicAnimation using the inherited animationWithKeyPath: method, specifying the key path of the property to be animated in the render tree.

Setting Interpolation Values

The fromValue, byValue and toValue properties define the values being interpolated between. All are optional, and no more than two should be non-nil. The object type should match the type of the property being animated.

The interpolation values are used as follows:

• Both fromValue and toValue are non-nil. Interpolates between fromValue and toValue.

• fromValue and byValue are non-nil. Interpolates between fromValue and (fromValue + byValue).

• byValue and toValue are non-nil. Interpolates between (toValue - byValue) and toValue.

• fromValue is non-nil. Interpolates between fromValue and the current presentation value of the property.

• toValue is non-nil. Interpolates between the current value of keyPath in the target layer‚Äôs presentation layer and toValue.

• byValue is non-nil. Interpolates between the current value of keyPath in the target layer‚Äôs presentation layer and that value plus byValue.

• All properties are nil. Interpolates between the previous value of keyPath in the target layer‚Äôs presentation layer and the current value of keyPath in the target layer‚Äôs presentation layer.