objective-c - 从KVO中检索 `change`字典中的信息

Question

方法

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
}

有一个参数change，它是一个字典，其中包含有关值更改性质的信息，我如何找出该字典中的内容？

Answer 1

这是 keys used by the change dictionary 的列表.

摘录:

Keys used by the change dictionary

These constants are used as keys in the change dictionary passed to observeValueForKeyPath:ofObject:change:context:.

NSString *const NSKeyValueChangeKindKey;
NSString *const NSKeyValueChangeNewKey;
NSString *const NSKeyValueChangeOldKey;
NSString *const NSKeyValueChangeIndexesKey;
NSString *const NSKeyValueChangeNotificationIsPriorKey;