神奇的記錄，不能保存對象：contextDidSave == NO，誤差=零

Question

我想堅持新的實體：

- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion { 
    NSMutableArray *mutableArray = [NSMutableArray array]; 

    [Quiz MR_truncateAll]; 
    [[NSManagedObjectContext MR_context] MR_saveWithBlock:^(NSManagedObjectContext *localContext) { 

     for (NSDictionary *dictionary in quizzess) { 
      Quiz *quiz = [Quiz MR_createEntity]; 
      [quiz fromDictionary:dictionary]; 
      [mutableArray addObject:quiz]; 
     } 
    } completion:^(BOOL contextDidSave, NSError *error) { 
     BlockSafeRun(completion, mutableArray, contextDidSave, error); 
    }]; 
} 

或者這樣：

- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion { 
    NSMutableArray *mutableArray = [NSMutableArray array]; 

    [Quiz MR_truncateAll]; 

    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) { 
     for (NSDictionary *dictionary in quizzess) { 
      Quiz *quiz = [Quiz MR_createEntity]; 
      [quiz fromDictionary:dictionary]; 
      [mutableArray addObject:quiz]; 
     } 
    } completion:^(BOOL contextDidSave, NSError *error) { 
     BlockSafeRun(completion, mutableArray, contextDidSave, error); 
    }]; 
} 

但在完成塊我收到contextDidSave == NO，錯誤== nil。 所以我無法弄清楚出了什麼問題。 我做了一些明顯的錯誤嗎？我該如何調試該問題？從MR

//////

2015-06-17 20:39:27.061 HITO[6733:618953] Set root saving context: <NSManagedObjectContext: 0x16dbe070> 
2015-06-17 20:39:27.062 HITO[6733:618953] Created new main queue context: <NSManagedObjectContext: 0x16e855b0> 
2015-06-17 20:39:27.063 HITO[6733:618953] Set default context: <NSManagedObjectContext: 0x16e855b0> 
2015-06-17 20:39:27.316 HITO[6733:618953] [HockeySDK] WARNING: Detecting crashes is NOT enabled due to running the app with a debugger attached. 
2015-06-17 20:39:28.829 HITO[6733:618953] Created new private queue context: <NSManagedObjectContext: 0x16d57870> 
2015-06-17 20:39:28.831 HITO[6733:619027] Created new private queue context: <NSManagedObjectContext: 0x16ea4ec0> 
2015-06-17 20:39:28.841 HITO[6733:619027] NO CHANGES IN ** saveWithBlock:completion: ** CONTEXT - NOT SAVING 

更新

以下代碼：

- (void) MR_saveWithOptions:(MRSaveOptions)saveOptions completion:(MRSaveCompletionHandler)completion; 
{ 
    __block BOOL hasChanges = NO; 

    if ([self concurrencyType] == NSConfinementConcurrencyType) 
    { 
     hasChanges = [self hasChanges]; 
    } 
    else 
    { 
     [self performBlockAndWait:^{ 
      hasChanges = [self hasChanges]; 
     }]; 
    } 

    if (!hasChanges) 
    { 
     MRLogVerbose(@"NO CHANGES IN ** %@ ** CONTEXT - NOT SAVING", [self MR_workingName]); 

     if (completion) 
     { 
      dispatch_async(dispatch_get_main_queue(), ^{ 
       completion(NO, nil); 
      }); 
     } 

     return; 
    } 

所以，hasChanges返回NO。

Answer 1

您的對象在保存塊中沒有發生變化。我在這裏看到兩個問題。

1. 當你需要在localContext這是您的保存塊保存上下文中創造他們你正在創建的MR_defaultContext你的新對象。

試試這個：

- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion { 
    NSMutableArray *mutableArray = [NSMutableArray array]; 


    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) { 
     for (NSDictionary *dictionary in quizzess) { 
      Quiz *quiz = [Quiz MR_createInContext:localContext]; 
      [quiz fromDictionary:dictionary]; 
      [mutableArray addObject:quiz]; 
     } 
    } completion:^(BOOL contextDidSave, NSError *error) { 
     BlockSafeRun(completion, mutableArray, contextDidSave, error); 
    }]; 
} 

你的對象是你開始導入新對象之前，實際上沒有被刪除。這可能不會導致你的上下文沒有改變，但我也會討論這個。

[Quiz MR_truncateAll]只是將所有的Quiz對象的deleted屬性true。這意味着下次保存或處理上下文時，更改將被保存。

因此，當您創建新的保存上下文時，上下文仍然具有這些對象。我不確定你的fromDictionary方法在做什麼，但是如果它依賴於一個數據庫，那麼它不會擁有它。

你需要做的是這樣的：

- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion { 
    NSMutableArray *mutableArray = [NSMutableArray array]; 


    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) { 
     [Quiz MR_truncateAllInContext:localContext]; 
     [localContext processPendingChanges]; 

     for (NSDictionary *dictionary in quizzess) { 
      Quiz *quiz = [Quiz MR_createInContext:localContext]; 
      [quiz fromDictionary:dictionary]; 
      [mutableArray addObject:quiz]; 
     } 
    } completion:^(BOOL contextDidSave, NSError *error) { 
     BlockSafeRun(completion, mutableArray, contextDidSave, error); 
    }]; 
} 

這樣一來，你在儲蓄方面刪除的對象。您還必須記得在保存上下文時調用processPendingChanges以從上下文中刪除對象，而不是將其標記爲要刪除。