ios – 核心数据：删除添加对象时出错

概述当我想通过下载和解析json文件来更新我的Core Data文件时,我的应用程序有时会崩溃.我收到以下错误： CoreData: error: Serious application error. Exception was caught during Core Data change processing. This is usually a bug within an observer of 当我想通过下载和解析Json文件来更新我的Core Data文件时,我的应用程序有时会崩溃.我收到以下错误：

CoreData: error: SerIoUs application error. Exception was caught
during Core Data change processing. This is usually a BUG within an
observer of NSManagedobjectContextObjectsDIDChangeNotification.
-[__NSCFSet addobject:]: attempt to insert nil with userInfo (null)

如果我在迭代期间更改属性,在迭代中保存NSManagedobjectContext的位置是否重要？

这是我的代码：

- (voID) updateData{               dispatch_queue_t serialdQueue;    serialdQueue = dispatch_queue_create("update",NulL);    dispatch_async(serialdQueue,^{        [self method1];    });    dispatch_async(serialdQueue,^{        [self method2];    });    dispatch_async(serialdQueue,^{        [self method3];    });    dispatch_async(serialdQueue,^{        [self method4];    });    dispatch_async(serialdQueue,^{        [self method5];    });}-(voID)method1{            //DOWNLOAD JsON file}-(voID)method2 //here i add objects to the core data file{            @try {        for (NSDictionary *JsonActivity in [Json objectForKey:@"ActivitIEs"]) {  //IteraTE THROUGH JsON ACTIVITY ARRAY            NSFetchRequest *request = [[NSFetchRequest alloc] init];            NSEntityDescription *entity = [NSEntityDescription entityForname:@"Activity" inManagedobjectContext:self.managedobjectContext];            [request setEntity:entity];            nspredicate *searchFilter = [nspredicate predicateWithFormat:@"Title == %@",[JsonActivity objectForKey:@"Title"]]; // CHECK IF OBJECT FROM JsON file ALREADY EXISTS...            [request setPredicate:searchFilter];            NSError *error = nil;            NSArray *results = [self.managedobjectContext executeFetchRequest:request error:&error];            if (error) {                NSLog(@"Error %@",error);                abort();            }            if ([results count] == 0) { // ADD NEW ACTIVITY IF olD List DOESNT CONTAIN IT                Activity *activity = [NSEntityDescription insertNewObjectForEntityForname:@"Activity" inManagedobjectContext:self.managedobjectContext];                activity.Title = [JsonActivity objectForKey:@"Title"];                activity.remove = [NSNumber numberWithBool:NO]; // REMOVE FLAG = NO BECAUSE NEW OBJECTS AREN'T REMOVED            } else  {                Activity *activity = (Activity*) [results objectAtIndex:0];                activity.remove = [NSNumber numberWithBool:NO]; // IF OBJECT ALREADY EXISTS IT SHOulD BE OBTAINED            }            AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];            [appDelegate saveContext]; // SAVE MO CONTEXT        }    }   @catch (NSException *exception) {        NSLog(@"Exception: %@",exception);    }}-(voID)method3 // DELETE olD OBJECTS {       NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];    NSEntityDescription *entityDescription = [NSEntityDescription entityForname:@"Activity" inManagedobjectContext:self.managedobjectContext];    [fetchRequest setEntity:entityDescription];    nspredicate *searchFilter = [nspredicate predicateWithFormat:@"remove == %@",[NSNumber numberWithBool:YES]];    [fetchRequest setPredicate:searchFilter];    NSArray *objectsToDelete = [[NSArray alloc] init];    NSError *error = nil;    objectsToDelete = [self.managedobjectContext executeFetchRequest:fetchRequest error:&error];    if (error) {        NSLog(@"Error %@",error);        abort();    }    for (Activity *activity in objectsToDelete) { // DELETE OBJECTS WITH THE PROPERTY REMOVE = YES        [self.managedobjectContext deleteObject:activity]; // DELETE ACTIVITY    }    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];    [appDelegate saveContext]; // SAVE MO CONTEXT}-(voID)method4 // CHANGE THE REMOVE PROPERTY TO YES OF ALL OBJECTS{            NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];    NSEntityDescription *entityDescription = [NSEntityDescription entityForname:@"Activity" inManagedobjectContext:self.managedobjectContext];    [fetchRequest setEntity:entityDescription];    NSArray *objects = [[NSArray alloc] init];    NSError *error = nil;    objects = [self.managedobjectContext executeFetchRequest:fetchRequest error:&error];    if (error) {        NSLog(@"Error %@",error);        abort();    }    for (Activity *activity in objects) {        activity.remove = [NSNumber numberWithBool:YES];    }    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];    [appDelegate saveContext]; // SAVE MO CONTEXT    NSLog(@"End Update");}-(voID)method5 //UPDATE UI{    //UI UPDATES}

解决方法 您不应该在serialQueue上访问托管对象上下文.看一下 NSManagedObjectContext documentation的Concurrency部分.

如果在您的代码中您的上下文使用的是nsprivateQueueConcurrencyType或NSMainQueueConcurrencyType并发类型,则可以使用其中一种基于块的方法来确保您处于正确的队列中：

//asyncrhonous[self.managedobjectContext performBlock:^{    //do stuff with the context}];//syncrhonous[self.managedobjectContext performBlockAnDWait:^{    //do stuff with the context}];

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