摘要：
赋值 赋值//可以修改私有成员变量-（void）setValue:（id）valueforKey:（NSString*）key-（void）setValuesForKeysWithDictionary:（NSDictionary*）keyedValues；Value//可以获取私有成员变量-（id）的值
// 能修改私有成员变量
- (void)setValue:(id)value forKey:(NSString *)key;
- (void)setValue:(id)value forKeyPath:(NSString *)keyPath;
- (void)setValuesForKeysWithDictionary:(NSDictionary *)keyedValues;
取值// 能取得私有成员变量的值
- (id)valueForKey:(NSString *)key;
- (id)valueForKeyPath:(NSString *)keyPath;
- (NSDictionary *)dictionaryWithValuesForKeys:(NSArray *)keys;
KVO:Key Value Observing 键值监听使用步骤:
1>.添加监听器
// 利用b对象来监听a对象name属性的改变
[a addObserver:b forKeyPath:@"name" options:NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew context:@"test"];
2>.在监听器中实现监听方法
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"%@ %@ %@ %@", object, keyPath, change, context);
}