Question

我已成功为我的keyPath @“isFinished”实现了KVO，但是我无法对其他属性执行相同的操作：isOfflineContentNil; 它的变化没有登记。

对象：

@property (nonatomic) BOOL isFinished;
@property (nonatomic) BOOL isOfflineContentNil;

@end

@implementation DataManager

-(instancetype)init {

  self = [super init];

  if (self) {
    [[NSUserDefaults standardUserDefaults] setObject:@[@{@"website" : @"TechCrunch", @"title" : @"New iPhone comming", @"authors" : @"some", @"date" : @"06/08/2014"},@{@"website" : @"TheVerge", @"title" : @"Macbook line refreshed", @"authors" : @"john", @"date" : @"16/09/2014"}] forKey:@"savedNews"];
    self.isOfflineContentNil = YES;

    NSMutableArray *userDefault = [[NSUserDefaults standardUserDefaults] objectForKey:@"savedNews"];

    if (userDefault) {
      self.savedForLaterNews = userDefault;
      self.isOfflineContentNil = NO;
    }

    dispatch_async(kBgQueue, ^{
      NSData *data = [NSData dataWithContentsOfURL:kLatestNewsURL];
      [self performSelectorOnMainThread:@selector(fetchedData:) withObject:data waitUntilDone:YES];
    });

    self.isFinished = NO;
  }

  return self;
}

-(void)fetchedData:(NSData *)responseData {

  NSError *error;

  self.json = [NSJSONSerialization JSONObjectWithData:responseData
                                              options:kNilOptions
                                                error:&error];
  self.currentNews = [self.json mutableCopy];
  self.isFinished = YES;
  [self sortJSONInformation];

}

监听器：

self.dataManager = [DataManager new];
  [self.dataManager addObserver:self forKeyPath:@"isFinished" options:NSKeyValueObservingOptionOld context:nil];
  [self.dataManager addObserver:self forKeyPath:@"isOfflineContentNil" options:NSKeyValueObservingOptionOld context:nil];
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
                       change:(NSDictionary *)change context:(void *)context {

  if ([keyPath isEqualToString:@"isFinished"]) {

    [self animateViewDismiss:self.loadingView];
  } else if ([keyPath isEqualToString:@"isOfflineContentNil"]) {

    self.isCurrentNews = NO;
    [self animateViewDismiss:self.loadingView];
  } else {
    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
  }
}

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Answer 1

发现我需要将观察选项修改为

options:NSKeyValueObservingOptionInitial

非常罕见，但适用于这种情况。

无法实现KVO来跟踪BOOL属性

1 个答案: