objc学习摘录

KVO使用的方法

/** 
 * Used by Foundation's Key-Value Observing.
 * 
 * @warning Do not call this function yourself.
 */
OBJC_EXPORT Class objc_duplicateClass(Class original, const char *name, size_t extraBytes)
     __OSX_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0);

UIViewController

[self addObserver:self forKeyPath:@"intValue" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];
self.intValue = 1230;

/// 一般的属性也会触发该方法调用 storyboard mswitch psegment sswitch view
- (void)setValue:(id)value forKeyPath:(NSString *)keyPath {
    [super setValue:value forKeyPath:keyPath];
    NSLog(@"通过KVC设置值key：%@", keyPath);
}
/// 一般的属性也会触发该方法调用 storyboard mswitch psegment sswitch view
- (void)setValue:(id)value forKey:(NSString *)key {
    [super setValue:value forKey:key];
    NSLog(@"设置Key-Value对key：%@", key);
}
/// 这个函数在调用addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:之后对应属性变化才会调用
- (void)didChangeValueForKey:(NSString *)key {
    NSLog(@"已经改变key：%@",key);
    [super didChangeValueForKey:key];
}

/// 这个函数在调用addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:之后对应属性变化才会调用
- (void)willChangeValueForKey:(NSString *)key {
    NSLog(@"即将改变key：%@",key);
    [super willChangeValueForKey:key];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    NSLog(@"接收到消息改变key：%@
%@",keyPath,change);
}