objective-c - KVO nsmutablearray 删除对象通知

Question

我有一个带有nsmutablearray的单例类

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    NSLog(@"Received notification: keyPath:%@ ofObject:%@ change:%@",
          keyPath, object, change);

    //[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];

}
//array accessors
- (void)insertNewObject:(id)object
{
    [self willChangeValueForKey:@"heldJoins"];
    [heldJoins addObject:object];
    [self didChangeValueForKey:@"heldJoins"];
}
- (void)removeObject:(id)object
{
    [self willChangeValueForKey:@"heldJoins"];
    [heldJoins removeObject:object];
    [self didChangeValueForKey:@"heldJoins"];
}

我“观察”另一个类对此数组所做的更改 我的 Root View Controller

    [CCV addObserver:self forKeyPath:@"heldJoins" options:NSKeyValueChangeOldKey||NSKeyValueChangeNewKey context:NULL];

}    
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
    {    
        NSLog(@"Received notification: keyPath:%@ ofObject:%@ change:%@",keyPath, object, [change allKeys]);
    }

这有效，当删除或添加对象时我会收到通知 但是我无法弄清楚(也许不可能)如何查看已删除或添加的对象(主要需要删除时未添加的对象)

我知道NSDictionary变量Change应该有我的对象，但它所拥有的只是一个键“种类”，它总是等于1，因为总是对对象进行1次更改数组。

nsmutablearray 填充了数字 500,100,300 因此，当其中一个数字被删除时，我想知道在我的观察者类中删除了哪个数字 我该怎么做？

应答代码:

[CCV addObserver:self forKeyPath:@"heldJoins" options: NSKeyValueObservingOptionOld ||NSKeyValueChangeNewKey context:NULL];

NSLog(@"Received notification: keyPath:%@ ofObject:%@ change:%@",keyPath, object, [change valueForKey:@"new"]);

Answer 1

听起来您在添加观察者时没有指定 NSKeyValueObservingOptionOld。