我使用的是AppDelegate的默认managedObjectContext，当我在其上使用executeFetchRequest时，它永远不会移至下一行或因错误而崩溃。它在后台线程上，因此UI不会冻结，但是数据永远不会填充-我的 Activity 指示器永远不会停止，调试会告诉我它永远不会退出该语句。我逐步完成每一行，并将其范围缩小到executeFetchRequest方法。是什么原因造成的？没有保存任何对象，但我认为这与它无关。到目前为止，已经一个小时了，所以显然有什么地方出错了。最后，这只发生了40％的时间。
代码如下所示:
NSSortDescriptor *byTimestamp = [NSSortDescriptorWithKey:@"timestamp" ascending:NO];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Message"];
[fetchRequest setSortDescriptors:@[byTimestamp]];
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
NSArray *messages = [managedObjectContext executeFetchRequest:fetchRequest error:&error];//hangs on this line!!
if(error != nil)
NSLog(@"Error: %@", [error localizedDescription]);
这是我的回溯:
* thread #1: tid = 0x1c03, 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10, stop reason = signal SIGSTOP
frame #0: 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #1: 0x9329ccb0 libsystem_kernel.dylib`mach_msg + 68
frame #2: 0x02488a49 CoreFoundation`__CFRunLoopServiceMachPort + 185
frame #3: 0x0248d84b CoreFoundation`__CFRunLoopRun + 1243
frame #4: 0x0248cf44 CoreFoundation`CFRunLoopRunSpecific + 276
frame #5: 0x0248ce1b CoreFoundation`CFRunLoopRunInMode + 123
frame #6: 0x029637e3 GraphicsServices`GSEventRunModal + 88
frame #7: 0x02963668 GraphicsServices`GSEventRun + 104
frame #8: 0x0041165c UIKit`UIApplicationMain + 1211
frame #9: 0x000027ad qub`main(argc=1, argv=0xbffff418) + 141 at main.m:16
thread #3: tid = 0x2203, 0x932a09ca libsystem_kernel.dylib`kevent64 + 10
frame #0: 0x932a09ca libsystem_kernel.dylib`kevent64 + 10
frame #1: 0x01c8cc2b libdispatch.dylib`_dispatch_mgr_invoke + 863
frame #2: 0x01c8c8cc libdispatch.dylib`_dispatch_mgr_thread + 61
thread #4: tid = 0x2303, 0x932a00ee libsystem_kernel.dylib`__workq_kernreturn + 10
frame #0: 0x932a00ee libsystem_kernel.dylib`__workq_kernreturn + 10
frame #1: 0x9017904c libsystem_c.dylib`_pthread_workq_return + 45
frame #2: 0x90178e19 libsystem_c.dylib`_pthread_wqthread + 448
thread #5: tid = 0x2403, 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #0: 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #1: 0x9329ccb0 libsystem_kernel.dylib`mach_msg + 68
frame #2: 0x02488a49 CoreFoundation`__CFRunLoopServiceMachPort + 185
frame #3: 0x0248d8d4 CoreFoundation`__CFRunLoopRun + 1380
frame #4: 0x0248cf44 CoreFoundation`CFRunLoopRunSpecific + 276
frame #5: 0x0248ce1b CoreFoundation`CFRunLoopRunInMode + 123
frame #6: 0x055ad310 WebCore`RunWebThread(void*) + 608
frame #7: 0x90176557 libsystem_c.dylib`_pthread_start + 344
thread #8: tid = 0x2703, 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #0: 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #1: 0x9329ccb0 libsystem_kernel.dylib`mach_msg + 68
frame #2: 0x02488a49 CoreFoundation`__CFRunLoopServiceMachPort + 185
frame #3: 0x0248d8d4 CoreFoundation`__CFRunLoopRun + 1380
frame #4: 0x0248cf44 CoreFoundation`CFRunLoopRunSpecific + 276
frame #5: 0x0248ce1b CoreFoundation`CFRunLoopRunInMode + 123
frame #6: 0x00ec7c7c Foundation`-[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 298
frame #7: 0x00ec7b45 Foundation`-[NSRunLoop(NSRunLoop) run] + 82
frame #8: 0x00085c60 qub`+[AFURLConnectionOperation networkRequestThreadEntryPoint:](self=0x000d2f1c, _cmd=0x000af418, object=0x00000000) + 304 at AFURLConnectionOperation.m:195
frame #9: 0x00f150d5 Foundation`-[NSThread main] + 76
frame #10: 0x00f15034 Foundation`__NSThread__main__ + 1304
frame #11: 0x90176557 libsystem_c.dylib`_pthread_start + 344
thread #9: tid = 0x2803, 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #0: 0x9329d7d2 libsystem_kernel.dylib`mach_msg_trap + 10
frame #1: 0x9329ccb0 libsystem_kernel.dylib`mach_msg + 68
frame #2: 0x02488a49 CoreFoundation`__CFRunLoopServiceMachPort + 185
frame #3: 0x0248d8d4 CoreFoundation`__CFRunLoopRun + 1380
frame #4: 0x0248cf44 CoreFoundation`CFRunLoopRunSpecific + 276
frame #5: 0x0248ce1b CoreFoundation`CFRunLoopRunInMode + 123
frame #6: 0x00fccebe Foundation`+[NSURLConnection(Loader) _resourceLoadLoop:] + 393
frame #7: 0x00f150d5 Foundation`-[NSThread main] + 76
frame #8: 0x00f15034 Foundation`__NSThread__main__ + 1304
frame #9: 0x90176557 libsystem_c.dylib`_pthread_start + 344
thread #10: tid = 0x2903, 0x9329fbe6 libsystem_kernel.dylib`select$DARWIN_EXTSN + 10
frame #0: 0x9329fbe6 libsystem_kernel.dylib`select$DARWIN_EXTSN + 10
frame #1: 0x024cacb7 CoreFoundation`__CFSocketManager + 1255
frame #2: 0x90176557 libsystem_c.dylib`_pthread_start + 344
thread #11: tid = 0x2a03, 0x9329f91a libsystem_kernel.dylib`__psynch_mutexwait + 10
frame #0: 0x9329f91a libsystem_kernel.dylib`__psynch_mutexwait + 10
frame #1: 0x9017c13b libsystem_c.dylib`pthread_mutex_lock + 595
frame #2: 0x014cdb01 CoreData`-[_PFLock lock] + 33
frame #3: 0x014cdada CoreData`-[NSPersistentStoreCoordinator lock] + 42
frame #4: 0x014e257e CoreData`-[NSPersistentStoreCoordinator executeRequest:withContext:error:] + 1182
frame #5: 0x014e09c9 CoreData`-[NSManagedObjectContext executeFetchRequest:error:] + 569
frame #6: 0x000492fe qub`__36-[RIPConvosViewController pullData:]_block_invoke(.block_descriptor=0x118e9320, newMessages=0x00000000, oldMessages=0x00000000) + 638 at RIPConvosViewController.m:73
frame #7: 0x00048fb4 qub`-[RIPConvosViewController pullData:](self=0x075293d0, _cmd=0x000abda7, completion=0xb0375ef0) + 212 at RIPConvosViewController.m:103
frame #8: 0x0004bab8 qub`__40-[RIPConvosViewController refreshTable:]_block_invoke(.block_descriptor=0x118d2e50) + 168 at RIPConvosViewController.m:236
frame #9: 0x01c8753f libdispatch.dylib`_dispatch_call_block_and_release + 15
frame #10: 0x01c99014 libdispatch.dylib`_dispatch_client_callout + 14
frame #11: 0x01c8a2e8 libdispatch.dylib`_dispatch_root_queue_drain + 335
frame #12: 0x01c8a450 libdispatch.dylib`_dispatch_worker_thread2 + 39
frame #13: 0x90178e12 libsystem_c.dylib`_pthread_wqthread + 441
顺便说一句，此代码位于RIPConvosViewController类的pullData方法的名为fetchBlock的块中。
我相信这是一个线程问题，但是我不知道如何解决这个问题-我应该确保对Core Data的所有调用都在同一线程上吗？如果这是解决方案，我该怎么办？
最佳答案
我有同样的问题，并检查了这个线程:executeFetchRequest:error: freezes app
我通过将NSManagedObjectContext请求放在@synchronized块中解决了该问题。
我的代码是:
-(void)saveBookmarksToCache:(NSMutableArray *) bookmarkList error:(NSError **)error
{
NSFetchRequest *allBookmarks = [[NSFetchRequest alloc] init];
[allBookmarks setEntity:self.bookmarkDescription];
[allBookmarks setIncludesPropertyValues:NO]; // Just fetch the Id
__autoreleasing NSError *reqError = nil;
NSArray *bookmarks = [self.managedObjectContext executeFetchRequest:allBookmarks error:&reqError];
if (reqError != nil)
error = &reqError;
...
// Save
[self.managedObjectContext save:&reqError];
...
}
并且它一直挂在executeFetchRequest行上(我有几个类或多或少同时执行相同类型的过程)。
正如另一个线程所建议的那样，我将其转换为:
-(void)saveBookmarksToCache:(NSMutableArray *) bookmarkList error:(NSError **)error
{
NSFetchRequest *allBookmarks = [[NSFetchRequest alloc] init];
[allBookmarks setEntity:self.bookmarkDescription];
[allBookmarks setIncludesPropertyValues:NO]; // Just fetch the Id
__autoreleasing NSError *reqError = nil;
// Lock the PersistenStoreCoordinator for the whole process
@synchronized(self.persistentStoreCoordinator) {
NSArray *bookmarks = [self.managedObjectContext executeFetchRequest:allBookmarks error:&reqError];
if (reqError != nil)
error = &reqError;
...
// Save
[self.managedObjectContext save:&reqError];
...
}
}
它似乎为我解决了这个问题。
关于ios - executeFetchRequest挂起，从不返回错误或继续，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/18544278/