Core data UIManagedDocument-如何处理UIDocumentStateSavingError？

我正在开发我的第一个iCloud应用程序。工作一段时间后，由于“UIDocumentStateSavingError”，应用程序无法再访问UIManagedDocument。有没有办法真正找出发生了什么错误

这是我创建UIManagedDocument的代码：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    iCloudURL = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];

    if (iCloudURL == nil) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [self iCloudNotAvailable];
        });
        return;
    }


    iCloudDocumentsURL = [iCloudURL URLByAppendingPathComponent:@"Documents"];
    iCloudCoreDataLogFilesURL = [iCloudURL URLByAppendingPathComponent:@"TransactionLogs"];

    NSURL *url = [iCloudDocumentsURL URLByAppendingPathComponent:@"CloudDatabase"];
    iCloudDatabaseDocument = [[UIManagedDocument alloc] initWithFileURL:url];

    NSMutableDictionary *options = [NSMutableDictionary dictionary];

    NSString *name = [iCloudDatabaseDocument.fileURL lastPathComponent];
    [options setObject:name forKey:NSPersistentStoreUbiquitousContentNameKey];
    [options setObject:iCloudCoreDataLogFilesURL forKey:NSPersistentStoreUbiquitousContentURLKey];

    iCloudDatabaseDocument.persistentStoreOptions = options;

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(documentContentsChanged:) name:NSPersistentStoreDidImportUbiquitousContentChangesNotification object:iCloudDatabaseDocument.managedObjectContext.persistentStoreCoordinator];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(documentStateChanged:) name:UIDocumentStateChangedNotification object:iCloudDatabaseDocument];


    if ([[NSFileManager defaultManager] fileExistsAtPath:[iCloudDatabaseDocument.fileURL path]]) {
        // This is true, the document exists.
        if (iCloudDatabaseDocument.documentState == UIDocumentStateClosed) {
            [iCloudDatabaseDocument openWithCompletionHandler:^(BOOL success) {
                if (success) {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        [self documentConnectionIsReady];
                    });
                } else {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        [self connectionError:iCloudConnectionErrorFailedToOpen];
                    });
                }
            }];                    
        } else if (iCloudDatabaseDocument.documentState == UIDocumentStateNormal) {
            ...
        }      
    } else {
        ...               
    }           
});

该文档已存在，因此对该文档调用openWithCompletionHandler:。此操作失败，并触发UIDocumentStateChangedNotification，显示文档状态为5： UIDocumentStateClosed和 UIDocumentStateSavingError

在此之后，将调用完成块。从这里出发的正确方法是什么？有没有办法找出哪里出了问题，发生了什么样的错误

我试图在完成块中重新打开文档，但结果相同

我想我可以通过删除文件并重新创建来解决这个问题。但这显然不是一个选项，一旦应用程序将在商店中。我想知道出了什么问题，并给用户一个合适的方法来处理这个问题

我已经在这里检查了处理UIDocumentStateSavingError的其他问题（这些问题并不多），但似乎不适用于这里的问题

---

你知道我怎样才能找出问题所在吗？我无法相信API会告诉您“保存过程中出现了问题，但我不会告诉您是什么！”

您可以在完成处理程序中查询documentState。不幸的是，如果您想要得到确切的错误，唯一的方法是子类化并重写handleError:UserInteractionAllowed:

也许像这样的东西会有帮助（不用编译器徒手输入）

然后你可以这样创造它

iCloudDatabaseDocument = [[UIManagedDocument alloc] initWithFileURL:url];

        [iCloudDatabaseDocument openWithCompletionHandler:^(BOOL success) {
            if (success) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    [self documentConnectionIsReady];
                });
            } else {
                dispatch_async(dispatch_get_main_queue(), ^{
                    [self connectionError:iCloudConnectionErrorFailedToOpen
                                withError:iCloudDatabaseDocument.lastError];
                });
            }
        }];                    

在完成处理程序中使用它，如下所示

iCloudDatabaseDocument = [[UIManagedDocument alloc] initWithFileURL:url];

        [iCloudDatabaseDocument openWithCompletionHandler:^(BOOL success) {
            if (success) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    [self documentConnectionIsReady];
                });
            } else {
                dispatch_async(dispatch_get_main_queue(), ^{
                    [self connectionError:iCloudConnectionErrorFailedToOpen
                                withError:iCloudDatabaseDocument.lastError];
                });
            }
        }];                    

---

基于@JodyHagins优秀的代码片段，我创建了一个UIDocument子类

@interface SSDocument : UIDocument
- (void)openWithSuccess:(void (^)())successBlock
           failureBlock:(void (^)(NSError *error))failureBlock;
@end


@interface SSDocument ()
@property (nonatomic, strong) NSError *lastError;
@end

@implementation SSDocument

- (void)handleError:(NSError *)error userInteractionPermitted:(BOOL)userInteractionPermitted {
    self.lastError = error;
    [super handleError:error userInteractionPermitted:userInteractionPermitted];
}

- (void)clearLastError {
    self.lastError = nil;
}

- (void)openWithSuccess:(void (^)())successBlock failureBlock:(void (^)(NSError *error))failureBlock {
    NSParameterAssert(successBlock);
    NSParameterAssert(failureBlock);
    [self clearLastError];
    [self openWithCompletionHandler:^(BOOL success) {
        if (success) {
            successBlock();
        } else {
            NSError *error = self.lastError;
            [self clearLastError];
            failureBlock(error);
        }
    }];
}

@end