Objective c 关于KVO和方法的问题；observeValueForKeyPath“；

您能否帮助我理解observeValueForKeyPath方法：

这里调用observeValueForKeyPath似乎是因为我们更改了“键：earthquakeList”的值，但假设我们观察到了另一个键，如“地震新列表”

如果我们只有一个回调方法observeValueForKeyPath，我怎么知道观察到的第一个或第二个键已经改变了

[self addObserver:self forKeyPath:@"earthquakeList" options:0 context:NULL];
//...
- (void)insertEarthquakes:(NSArray *)earthquakes
{
    // this will allow us as an observer to notified (see observeValueForKeyPath)
    // so we can update our UITableView
    //
    [self willChangeValueForKey:@"earthquakeList"];
    [self.earthquakeList addObjectsFromArray:earthquakes];
    [self didChangeValueForKey:@"earthquakeList"];
}

// listen for changes to the earthquake list coming from our app delegate.
- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    [self.tableView reloadData];
}

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感谢在您的

observeValueForKeyPath:ofObject:change:context:

实现中的

keyPath

参数将告诉您哪个键已更改。因此，您可以执行以下操作：

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    if ([keyPath isEqualToString:@"key1"]) {
        // do something
    } else if ([keyPath isEqualToString:@"key2"]) {
        // do something else
    }
}