监听Array数组内容变化

定义一个类

@interface KVOMutableArray : NSObject
@property (nonatomic, strong)NSMutableArray *array;
@end

@implementation KVOMutableArray
- (instancetype)init {
if (self = [super init]) {
self.array = [NSMutableArray array];
}
return self;
}
@end

在另一个类中，将KVOMutableArray的实例作为属性

@property (nonatomic, strong)KVOMutableArray *selectedData;
// 添加观察者

[self addObserver:self forKeyPath:@"selectedData.array" options:NSKeyValueObservingOptionNew context:nil];
// 实现代理方法
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context {
NSLog(@"%@", change);

}
// 移除观察者
- (void)dealloc {
[self removeObserver:self forKeyPath:@"selectedData.array"];
}
// 注意：在引用selectedData.array的时候，不能直接self.selectedData.array.不然监听不到变化.应该[self.selectedData mutableArrayValueForKey:@"array"]

另注：很多帖子说要重写以下方法，但是我测试没有重写这些方法也可以。不知道这些方法的作用到底是什么，如果有看到这篇帖子并且知道的请告知，谢谢！

- (NSUInteger)countOfArray {

return self.array.count;

}

- (id)objectInArrayAtIndex:(NSUInteger)index {

return [self.array objectAtIndex:index];

}

- (void)insertObject:(id)object inArrayAtIndex:(NSUInteger)index {

[self.array insertObject:object atIndex:index];

}

- (void)removeObjectFromArrayAtIndex:(NSUInteger)index {

[self.array removeObjectAtIndex:index];

}

- (void)replaceObjectInArrayAtIndex:(NSUInteger)index withObject:(id)object {

[self.array replaceObjectAtIndex:index withObject:object];

}