从大型 JSON 加载核心数据导致应用程序崩溃

Posted 2023-03-05

【中文标题】从大型 JSON 加载核心数据导致应用程序崩溃

【英文标题】：Loading Core Data From Large JSON Causing App To Crash

【发布时间】：2013-01-25 02:32:16

【问题描述】：

我正在尝试从包含 170,000 多个字典的 JSON 文件填充 CoreData。 json 的解析很快，但是当我开始尝试添加到 CoreData 时，我阻塞了主线程很长时间，然后应用程序最终崩溃了。调用方法时崩溃 [UIDocument saveToUrl:forSaveOperation:completionHandler] 这是我的代码。如果有人知道导致它崩溃的原因或更有效的加载 CoreData 的方法，将不胜感激。

@property (nonatomic, strong) UIManagedDocument *wordDatabase;

- (void)viewWillAppear:(BOOL)animated
  
    [super viewWillAppear:animated];
    if (!self.wordDatabase) 
      NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
      url = [url URLByAppendingPathComponent:@"Word Database"];
      self.wordDatabase = [[UIManagedDocument alloc] initWithFileURL:url];
    
 

- (void)setWordDatabase:(UIManagedDocument *)wordDatabase
  
    if (_wordDatabase != wordDatabase) 
      _wordDatabase = wordDatabase;
      [self useDocument];
    
  

- (void)useDocument
  
    if (![[NSFileManager defaultManager] fileExistsAtPath:[self.wordDatabase.fileURL path]]) 
      // does not exist on disk, so create it
      [self.wordDatabase saveToURL:self.wordDatabase.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) 
          [self setupFetchedResultsController];
          [self prepopulateWordDatabaseWithDocument:self.wordDatabase];
       ];
     
  

- (void)prepopulateWordDatabaseWithDocument:(UIManagedDocument *)document
  
    dispatch_queue_t fetchQ = dispatch_queue_create("Word Fetcher", NULL);
    dispatch_async(fetchQ, ^
    //Fetch the words from the json file
    NSString *fileString = [[NSBundle mainBundle] pathForResource:@"words" ofType:@"json"];
    NSString *jsonString = [[NSString alloc] initWithContentsOfFile:fileString encoding:NSUTF8StringEncoding error: NULL];
    NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    NSError *error;
    NSArray *words = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];
    [document.managedObjectContext performBlock:^
        for (NSDictionary *dictionary in words)
        
            [Word wordFromDictionary:dictionary inManagedObjectContext:document.managedObjectContext];
        

        [document saveToURL:document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
      ];
    );

   dispatch_release(fetchQ);
 

【参考方案1】：

我最终阻止我的应用程序崩溃的是分配一个新的 NSManagedObjectContext 并在后台执行我的所有加载。保存后，我调用了我的 NSFetchedResultsController 并重新填充了表格。

- (void)prepopulateWordDatabaseWithDocument:(UIManagedDocument *)document
 
     NSManagedObjectContext *backgroundContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
     backgroundContext.undoManager = nil;
     backgroundContext.persistentStoreCoordinator = document.managedObjectContext.persistentStoreCoordinator;
     [backgroundContext performBlock:^
         NSString *fileString = [[NSBundle mainBundle] pathForResource:@"words" ofType:@"json"];
         NSString *jsonString = [[NSString alloc] initWithContentsOfFile:fileString encoding:NSUTF8StringEncoding error: NULL];
         NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
         NSError *parseError;
         NSArray *words = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&parseError];

         for (NSDictionary *dictionary in words)
         
             [Word wordFromDictionary:dictionary inManagedObjectContext:backgroundContext];
         

         NSError *loadError;
         if ([backgroundContext save:&loadError]) 
             dispatch_async(dispatch_get_main_queue(), ^
                 [self setupFetchedResultsController];
             );
         
     ];