[英]iOS exc_bad_access when observing NSUserDefaults with KVO and delayedSelector
I've encountered a weird bug and would like to check if I'm using my Key value observing of changes to NSUserDefaults correctly. 我遇到了一个奇怪的错误,想检查我是否使用我的Key值来正确观察NSUserDefaults的更改。
I have used this code in two places in my app without issues, then I added 3rd controller that observes values for "goldCount" and "energyCount". 我已经在我的应用程序中的两个地方使用了此代码,没有问题,然后添加了第三个控制器,用于观察“ goldCount”和“ energyCount”的值。 Now when I set the initial value, the app crashes with exc_bad_access.
现在,当我设置初始值时,应用程序因exc_bad_access而崩溃。 I'm adding this controller to the view 2 seconds after it's parent view appears using
performSelectorAfterDelay
. 我在使用
performSelectorAfterDelay
其父视图出现2秒后,将该控制器添加到视图中。
Just before displaying the game screen, I set these properties: 在显示游戏屏幕之前,我设置了以下属性:
//crash on this line
[[NSUserDefaults standardUserDefaults] setInteger:200 forKey: goldCount];
[[NSUserDefaults standardUserDefaults] setInteger:150 forKey: energyCount];
Within 3 different view controllers, I have this code in viewDidLoad: 在3个不同的视图控制器中,我在viewDidLoad中具有以下代码:
NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
[defaults addObserver:self
forKeyPath:@"goldCount"
options:NSKeyValueObservingOptionNew
context:NULL];
[defaults addObserver:self
forKeyPath:@"energyCount"
options:NSKeyValueObservingOptionNew
context:NULL];
self.goldLabel.text = [NSString stringWithFormat:@"%i",[[GameDataManager sharedInstance] currentGoldCount]];
self.energyLabel.text = [NSString stringWithFormat:@"%i",[[GameDataManager sharedInstance] currentEnergyCount]];
Here's how the class updates it's labels: 该类如何更新其标签:
// KVO handler
-(void)observeValueForKeyPath:(NSString *)aKeyPath ofObject:(id)anObject
change:(NSDictionary *)aChange context:(void *)aContext
{
//aKeyPath gives us the name of a user default that has changed
if([aKeyPath isEqualToString:@"goldCount"])
{
//we are interested in the new value
self.goldLabel.text = [NSString stringWithFormat:@"%i",[[aChange objectForKey:@"new"] intValue]];
}else if([aKeyPath isEqualToString:@"energyCount"])
{
self.energyLabel.text = [NSString stringWithFormat:@"%i",[[aChange objectForKey:@"new"] intValue]];
}
}
After adding a call to [[NSUserDefaults standardUserDefaults] synchronize]; 向[[NSUserDefaults standardUserDefaults]同步]添加呼叫后; I get this exception the second time around:
我第二次收到此异常:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '( ): An -observeValueForKeyPath:ofObject:change:context: message was received but not handled.
由于未捕获的异常'NSInternalInconsistencyException'而终止应用程序,原因:'():收到但未处理-observeValueForKeyPath:ofObject:change:context:消息。 Key path: goldCount Observed object: Change: { kind = 1;
关键路径:goldCount观察到的对象:更改:{kind = 1; new = 205;
新= 205; } Context: 0x0'
上下文:0x0'
NSUserDefaults is not documented to be KVO compliant so it's not possible to observe defaults by their key. 未记录NSUserDefaults是否兼容KVO,因此无法通过其键遵守默认值。 This might be the reason for the crash but without a stack trace it's not possible to tell.
这可能是导致崩溃的原因,但是如果没有堆栈跟踪就无法分辨。
There is a notification you can register for that announces changes to the defaults system: NSUserDefaultsDidChangeNotification
. 您可以注册一个通知,以宣布对默认系统的更改:
NSUserDefaultsDidChangeNotification
。
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