现在这可能听起来像我之前的问题/问题，但我已经改变并尝试了一些在我的其他问题中得到回答的东西，试图让它发挥作用，但我仍然遇到同样的问题。
我正在从 NSManagedObject 子类中观察核心数据属性，并且在属性更改时调用的方法调用另一个方法，但在此方法中，它添加了触发 KVO 方法的核心数据对象，该方法再次触发该方法等等。或者看起来，我不太确定，因为似乎发生了一些不同的事情，这是一系列事件......</p>
- 我单击一个与 iCal 同步的按钮（这在 IBAction 中，与方法 syncKVO 中的代码完全相同）。此同步工作正常。
- 我在大纲视图中添加了一个对象。一切都很好。
- 我更改了它的名称以触发与 iCal 同步的 KVO 声明（因为我更改了“名称”属性）。工作正常。
- 我删除了刚刚添加的对象，它以某种方式触发了 KVO 声明（从而触发了该方法）并将我置于无限循环中。
现在来看一些代码。
NSManagedObject 子类（称为 JGManagedObject）内的代码……</p>
- (void) awakeFromFetch {
[self addObserver:[NSApp delegate] forKeyPath:@"name" options:0 context:nil];
}
- (void) awakeFromInsert {
[self addObserver:[NSApp delegate] forKeyPath:@"name" options:0 context:nil];
}
+ (void) addObserver{
[self addObserver:[NSApp delegate] forKeyPath:@"name" options:0 context:nil];
}
+ (void) removeObserver{
[self removeObserver:[NSApp delegate] forKeyPath:@"name"];
}
KVO 声明（在 App Delegate 内）……</p>
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if ([keyPath isEqualToString:@"name"]) {
[self performSelector:@selector(syncKVO:)];
}
}
方法（也在 App Delegate 中）……</p>
- (void)syncKVO:(id)sender {
NSManagedObjectContext *moc = [self managedObjectContext];
[syncButton setTitle:@"Syncing..."];
NSString *dateText = (@"Last Sync : %d", [NSDate date]);
[syncDate setStringValue:dateText];
NSEntityDescription *entityDescription = [NSEntityDescription
entityForName:@"projects" inManagedObjectContext:moc];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entityDescription];
NSError *error = nil;
NSArray *array = [moc executeFetchRequest:request error:&error];
if (array == nil)
{
NSAlert *anAlert = [NSAlert alertWithError:error];
[anAlert runModal];
}
NSArray *namesArray = [array valueForKey:@"name"];
NSPredicate *predicate = [CalCalendarStore taskPredicateWithCalendars:[[CalCalendarStore defaultCalendarStore] calendars]];
NSArray *tasksNo = [[CalCalendarStore defaultCalendarStore] tasksWithPredicate:predicate];
NSArray *tasks = [tasksNo valueForKey:@"title"];
NSMutableArray *namesNewArray = [NSMutableArray arrayWithArray:namesArray];
[namesNewArray removeObjectsInArray:tasks];
NSLog(@"%d", [namesNewArray count]);
NSInteger *popIndex = [calenderPopup indexOfSelectedItem];
//Load the array
CalCalendarStore *store = [CalCalendarStore defaultCalendarStore];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
NSString *supportDirectory = [paths objectAtIndex:0];
NSString *fileName = [supportDirectory stringByAppendingPathComponent:@"oldtasks.plist"];
NSMutableArray *oldTasks = [[NSMutableArray alloc] initWithContentsOfFile:fileName];
[oldTasks removeObjectsInArray:namesArray];
NSLog(@"%d",[oldTasks count]);
//Use the content
NSPredicate* taskPredicate = [CalCalendarStore taskPredicateWithCalendars:[[CalCalendarStore defaultCalendarStore] calendars]];
NSArray* allTasks = [[CalCalendarStore defaultCalendarStore] tasksWithPredicate:taskPredicate];
// Get the calendar
CalCalendar *calendar = [[store calendars] objectAtIndex:popIndex];
// Note: you can change which calendar you're adding to by changing the index or by
// using CalCalendarStore's -calendarWithUID: method
// Loop, adding tasks
for(NSString *title in namesNewArray) {
// Create task
CalTask *task = [CalTask task];
task.title = title;
task.calendar = calendar;
// Save task
if(![[CalCalendarStore defaultCalendarStore] saveTask:task error:&error]) {
NSLog(@"Error");
// Diagnostic error handling
NSAlert *anAlert = [NSAlert alertWithError:error];
[anAlert runModal];
}
}
NSMutableArray *tasksNewArray = [NSMutableArray arrayWithArray:tasks];
[tasksNewArray removeObjectsInArray:namesArray];
NSLog(@"%d", [tasksNewArray count]);
for(NSString *title in tasksNewArray) {
NSManagedObjectContext *moc = [self managedObjectContext];
JGManagedObject *theParent =
[NSEntityDescription insertNewObjectForEntityForName:@"projects"
inManagedObjectContext:moc];
[theParent setValue:nil forKey:@"parent"];
// This is where you add the title from the string array
[theParent setValue:title forKey:@"name"];
[theParent setValue:[NSNumber numberWithInt:0] forKey:@"position"];
}
for(CalTask* task in allTasks)
if([oldTasks containsObject:task.title]) {
[store removeTask:task error:nil];
}
// Create a predicate for an array of names.
NSPredicate *mocPredicate = [NSPredicate predicateWithFormat:@"name IN %@", oldTasks];
[request setPredicate:mocPredicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
// Execute the fetch request put the results into array
NSArray *resultArray = [moc executeFetchRequest:request error:&error];
if (resultArray == nil)
{
// Diagnostic error handling
NSAlert *anAlert = [NSAlert alertWithError:error];
[anAlert runModal];
}
// Enumerate through the array deleting each object.
// WARNING, this will delete everything in the array, so you may want to put more checks in before doing this.
for (JGManagedObject *objectToDelete in resultArray ) {
// Delete the object.
[moc deleteObject:objectToDelete];
}
//Save the array
[namesArray writeToFile:fileName atomically:YES];
[syncButton setTitle:@"Sync Now"];
NSLog(@"Sync Completed");
}
我试过的……</p>
过滤调用 KVO 声明的键路径
if ([keyPath isEqualToString:@"name"]) {
…
}
分离和重新附加观察者
[JGManagedObject removeObserver];
//and
[JGManagedObject addObserver];
但是它第一次工作但第二次停止该方法说它不能删除观察者，因为它没有观察，这没有意义，因为我第一次再次添加了观察者。这就是为什么我将这段代码排除在实际方法之外，否则它会在第二次同步时停止。
我不确定这是怎么回事，我想我已经尝试了一切。出了什么问题？
任何帮助将不胜感激。