KVO - 观察枚举时未调用observeValueForKeyPath

发布于 2024-10-21 16:24:44 字数 1310 浏览 1 评论 0原文

我以前使用过 NSNotifications，但这是我第一次尝试在 Cocoa Touch 中使用 KVO。

我的 UITableView 控制器在各种数据源之间切换，因此我将它们封装在不同的 UITableViewDataSource 子类中。我试图让我的视图控制器观察这些 UITableViewDataSource 子类中的特定一个，并跟踪一个名为 loadState 的枚举，该枚举反映了模型的加载状态。

我这样设置观察者：

[self.siteUpdatesDataSource addObserver:self
                             forKeyPath:@"loadState"
                                options:0
                                context:nil];

从调试器中我可以看到观察者已注册：）

(gdb) po [self siteUpdatesDataSource]
<SiteUpdatesTableViewDataSource: 0x651e5a0>
Current language:  auto; currently objective-c
(gdb) po [[self siteUpdatesDataSource] observationInfo]
<NSKeyValueObservationInfo 0x651dd70> (
<NSKeyValueObservance 0x651dd10: Observer: 0xc80f1e0, Key path: loadState, Options: <New: NO, Old: NO, Prior: NO> Context: 0x0, Property: 0x651dd90>

但是

，我的 viewController 中的observeValueForKeyPath 方法似乎从未被调用。我设置了一个断点，即使我验证枚举已更改，也不会到达该断点。

- (void) observeValueForKeyPath:(NSString *)keyPath 
                        ofObject:(id)object
                          change:(NSDictionary *)change
                         context:(void *)context {

   [self.tableView reloadData];
}

我很感激对我所缺少的东西的任何想法。

原文

I've used NSNotifications before but this is the first time I've tried to use KVO in Cocoa Touch.

My UITableView controller switches between a variety of datasources so I've encapsulated them in different UITableViewDataSource subclasses. I'm trying to have my view controller observe a specific one of these UITableViewDataSource subclasses and track an enum called loadState that reflects the models the load state.

I set the observer like this:

[self.siteUpdatesDataSource addObserver:self
                             forKeyPath:@"loadState"
                                options:0
                                context:nil];

From the debugger I can see that the observer is registered:

(gdb) po [self siteUpdatesDataSource]
<SiteUpdatesTableViewDataSource: 0x651e5a0>
Current language:  auto; currently objective-c
(gdb) po [[self siteUpdatesDataSource] observationInfo]
<NSKeyValueObservationInfo 0x651dd70> (
<NSKeyValueObservance 0x651dd10: Observer: 0xc80f1e0, Key path: loadState, Options: <New: NO, Old: NO, Prior: NO> Context: 0x0, Property: 0x651dd90>

)

However, my observeValueForKeyPath method in my viewController never seems to be called. I set a breakpoint and nothing ever reaches it even when I validate that the enum has changed.

- (void) observeValueForKeyPath:(NSString *)keyPath 
                        ofObject:(id)object
                          change:(NSDictionary *)change
                         context:(void *)context {

   [self.tableView reloadData];
}

I appreciate any thoughts on what I'm missing.

分享到QQ

分享到微博