监听Array数组内容变化

1. 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

1. 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];

}