核心数据自定义迁移

Question

我的旧核心数据模型有一个NSDate字段，我想将其更改为NSNumber。我读苹果文档和SO几个类似的问题和其他博客（见问题的最终参考）

但无论我做什么，我不断收到同样的错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Mismatch between mapping and source/destination models'

我只有该模型的两个版本，并且我已经多次验证源模型和目标模型是正确的。

我甚至放弃了我的所有更改，并重新创建了一个新模型，映射和实体（NSManagedObject子类）。我一直在这个问题上停留了将近2天，并且不知道我在做什么。任何指针，我做错了将不胜感激。

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator { 
    if (_persistentStoreCoordinator != nil) { 
     return _persistentStoreCoordinator; 
    } 

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Old.sqlite"]; 

    NSError *error = nil; 
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; 

    NSString *sourceStoreType = NSSQLiteStoreType; 
    NSURL *sourceStoreURL = storeURL; 

    NSURL *destinationStoreURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"New.sqlite"]; 
    NSString *destinationStoreType = NSSQLiteStoreType; 
    NSDictionary *destinationStoreOptions = nil; 

    NSDictionary *sourceMetadata = 
    [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:sourceStoreType 
                   URL:sourceStoreURL 
                  error:&error]; 

    if (sourceMetadata == nil) { 
     NSLog(@"source metadata is nil"); 
    } 

    NSManagedObjectModel *destinationModel = [_persistentStoreCoordinator managedObjectModel]; 
    BOOL pscCompatibile = [destinationModel 
          isConfiguration:nil 
          compatibleWithStoreMetadata:sourceMetadata]; 

    if (pscCompatibile) { 
     // no need to migrate 
     NSLog(@"is compatible"); 
    } else { 
     NSLog(@"is not compatible"); 

     NSManagedObjectModel *sourceModel = 
     [NSManagedObjectModel mergedModelFromBundles:nil 
            forStoreMetadata:sourceMetadata]; 

     if (sourceModel != nil) { 
      NSLog(@"source model is not nil"); 

      NSMigrationManager *migrationManager = 
      [[NSMigrationManager alloc] initWithSourceModel:sourceModel 
              destinationModel:destinationModel]; 

      NSURL *fileURL = [[NSBundle mainBundle] URLForResource:@"MyMigrationMapping" withExtension:@"cdm"]; 
      NSMappingModel *mappingModel = [[NSMappingModel alloc] initWithContentsOfURL:fileURL]; 

      NSArray *newEntityMappings = [NSArray arrayWithArray:mappingModel.entityMappings]; 
      for (NSEntityMapping *entityMapping in newEntityMappings) { 
       entityMapping.entityMigrationPolicyClassName = NSStringFromClass([ConvertDateToNumberTransformationPolicy class]); 
      } 
      mappingModel.entityMappings = newEntityMappings; 

      BOOL ok = [migrationManager migrateStoreFromURL:sourceStoreURL 
                 type:sourceStoreType 
                options:nil 
              withMappingModel:mappingModel 
              toDestinationURL:destinationStoreURL 
              destinationType:destinationStoreType 
             destinationOptions:nil 
                 error:&error]; 

      if (ok) { 
       storeURL = destinationStoreURL; 
      } 
     } else { 
      NSLog(@"e nil source model"); 
     } 
    } 

    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: 
          [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, 
          [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, 
          nil]; 

    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) { 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
     abort(); 
    }  

    return _persistentStoreCoordinator; 
} 

我定制NSEntityMigration类：

- (BOOL)createDestinationInstancesForSourceInstance:(NSManagedObject *)sInstance 
             entityMapping:(NSEntityMapping *)mapping 
              manager:(NSMigrationManager *)manager 
               error:(NSError **)error 
{ 
    // Create a new object for the model context 
    NSManagedObject *newObject = 
    [NSEntityDescription insertNewObjectForEntityForName:[mapping destinationEntityName] 
            inManagedObjectContext:[manager destinationContext]]; 

    NSArray *arrayOfKeys = @[@"startDate", @"endDate", @"creationTime", @"timeStamp"]; 

    for (NSString *key in arrayOfKeys) { 
     // do our transfer of NSDate to NSNumber 
     NSDate *date = [sInstance valueForKey:key]; 
     NSLog(@"Key: %@, value: %@", key, [date description]); 

     // set the value for our new object 
     [newObject setValue:[NSNumber numberWithDouble:[date timeIntervalSince1970]] forKey:key]; 
    } 

    // do the coupling of old and new 
    [manager associateSourceInstance:sInstance withDestinationInstance:newObject forEntityMapping:mapping]; 

    return YES; 
} 

一些参考：

1. Example or explanation of Core Data Migration with multiple passes?
2. Core Data - Default Migration (Manual)
3. http://www.preenandprune.com/cocoamondo/?p=468
4. http://www.timisted.net/blog/archive/core-data-migration/

Answer 1

我承认我不明白错误的原因。在我的迁移中，每个实体都有一个策略，我在使用它之前检查实体。不知道这额外if将帮助您：

- (BOOL)createDestinationInstancesForSourceInstance:(NSManagedObject *)sInstance 
            entityMapping:(NSEntityMapping *)mapping 
             manager:(NSMigrationManager *)manager 
              error:(NSError **)error { 

    NSEntityDescription *sourceInstanceEntity = [sInstance entity]; 
    if ([[sInstance name] isEqualToString:@"<-name-of-entity>"]) { 
     newObject = [NSEntityDescription insertNewObjectForEntityForName:@"<-name-of-entity>" 
         inManagedObjectContext:[manager destinationContext]]; 
     NSArray *arrayOfKeys = @[@"startDate", @"endDate", @"creationTime", @"timeStamp"]; 

     for (NSString *key in arrayOfKeys) { 
      // do our transfer of NSDate to NSNumber 
      NSDate *date = [sInstance valueForKey:key]; 
      NSLog(@"Key: %@, value: %@", key, [date description]); 

      // set the value for our new object 
      [newObject setValue:[NSNumber numberWithDouble:[date timeIntervalSince1970]] forKey:key]; 
     } 
    } 

// do the coupling of old and new 
[manager associateSourceInstance:sInstance withDestinationInstance:newObject forEntityMapping:mapping]; 

return YES; 

}

Answer 2

一切你正在做的是方式复杂得多，它必须是。你可以做所有这些，而无需迁移你的数据库。您可以在其他属性添加到您的子类，实现它：

///in your .h 
@property(nonatomic, copy) NSNumber* startDateNumber 
/// in you .m 
-(NSNumber*) startDateNumber{ 
    if (self.startDate) { 
     return @(self.startDate.timeIntervalSince1970); 
    } 
    return nil; 
} 
-(void)setStartDateNumber:(NSNumber*)startDateNumber{ 
    if(startDateNumber){ 
     self.startDate =[NSDate dateWithTimeIntervalSince1970:startDateNumber.doubleValue]; 
    }else{ 
     self.startDate = nil; 
    } 
} 

这是一个有点恼人的有重复的属性（startDate和startDateNumber），但它是如此简单得多，并没有任何的迁移问题。