iphone - CoreData 应用程序在执行获取请求时卡住 pthread_mutex_lock

Question

我正在使用 Core Data 来管理我的应用程序中的数据库。

我无法在这里发布代码，因为它太长了。但我想我可以用一小行代码和一些快照来解释我的问题。

+(NSArray *)checkusernameandpassword:(NSString *)entityname  username:(NSString *)username   password:(NSString *)password 
{
    managedobjectcontext=[Singleton sharedmysingleton].managedobjectcontext;
    NSEntityDescription *entity=[NSEntityDescription entityForName:entityname inManagedObjectContext:managedobjectcontext];

    NSFetchRequest *request=[[NSFetchRequest alloc] init];
    [request setEntity:entity];

    NSPredicate *predicates=[NSPredicate predicateWithFormat:[NSString stringWithFormat:@"userName==\"%@\" AND password==\"%@\"",username,password]];
    [request setPredicate:predicates];  
    //On Below line, My app frezes and goes into deadlock, this happens randomly while performing
    //some data request using Core data
    NSArray *arrayofrecord=[managedobjectcontext executeFetchRequest:request error:nil];    

    return arrayofrecord;
}

我正在尝试附加一些调用堆栈的屏幕截图(这些是我在暂停应用程序时看到的)图中打勾的方法，就是上面提到的发生死锁的方法

Answer 1

您必须锁定线程。当多个线程访问同一段代码时就会出现这个问题。但我们最终不会陷入僵局。

static NSString *fetchRequest = @"fetchRequest";
    NSArray *results;
    @synchronized (fetchRequest){
        managedobjectcontext=[Singleton sharedmysingleton].managedobjectcontext;
        NSEntityDescription *entity=[NSEntityDescription entityForName:entityname inManagedObjectContext:managedobjectcontext];

        NSFetchRequest *request=[[NSFetchRequest alloc] init];
       [request setEntity:entity];

       NSPredicate *predicates=[NSPredicate predicateWithFormat:[NSString stringWithFormat:@"userName==\"%@\" AND password==\"%@\"",username,password]];
       [request setPredicate:predicates];  
       //On Below line, My app frezes and goes into deadlock, this happens randomly while performing
       //some data request using Core data
       results = [managedobjectcontext executeFetchRequest:request error:nil];    
}
return results;