Core Animation学习笔记—第十节Key-Value Coding Extensions

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今天2021年12月10日
这一章叫做Key-Value Coding Extensions

这章是附录，关于KVC的
Core Animaiton对KVO做了扩展
CAAnimation和CALAyer类是符合键值编码的容器类，这意味着您可以为任意键设置值。即使key someKey 不是 CALayer 类的声明属性，仍可按如下方式为其设置值：
layer.setValue(50,forKey:”someKey”)
取值一样

CAAnimation和CALayer类通过defaultValueForKey: 类方法设置默认值

Kvc支持结构体

CATransform3D Key Paths
You can use the enhanced key path support to retrieve specific transformation values for a property that contains a CATransform3D data type. To specify the full key path for a layer’s transforms, you would use the string value transform or sublayerTransform followed by one of the field key paths in Table C-2.

Setting values using key paths is not the same as setting them using Objective-C properties. You cannot use property notation to set transform values. You must use the setValue:forKeyPath: method with the preceding key path strings.

CGPoint Key Paths
If the value of a given property is a CGPoint data type, you can append one of the field names in Table C-3 to the property to get or set that value.

CGSize Key Paths
If the value of a given property is a CGSize data type, you can append one of the field names in Table C-4 to the property to get or set that value.
Table C-4 CGSize data structure fields

CGRect Key Paths
If the value of a given property is a CGRect data type, you can append the following field names in Table C-3 to the property to get or set that value. For example, to change the width component of a layer’s bounds property, you could write to the key path bounds.size.width.
Table C-5 CGRect data structure fields