“自动轻量级迁移”的实现核心数据（iPhone） [英] Implementation of "Automatic Lightweight Migration" for Core Data (iPhone)

问题描述

当我向我的核心数据模型添加
新属性时，我想让我的应用程序能够进行自动轻量级迁移。

从苹果这是唯一的信息，我可以找到的主题：

自动轻量级迁移

要请求自动轻量级
迁移，请在传递的选项字典中设置适当的标志

addPersistentStoreWithType：configuration：URL：options：error： 。
您需要将对应
的值设置为
NSMigratePersistentStoresAutomaticallyOption
和
NSInferMappingModelAutomaticallyOption
键为YES：

  NSError * error; 
 NSURL * storeURL =<＃持久性存储的URL＃> ;; 
 NSPersistentStoreCoordinator * psc =< #The coordinator＃> ;; 
 NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys：
 [NSNumber numberWithBool：YES]，NSMigratePersistentStoresAutomaticallyOption，
 [NSNumber numberWithBool：YES]，NSInferMappingModelAutomaticallyOption，nil]; 
 
 if（！[psc addPersistentStoreWithType：< #Store type＃> 
 configuration：< #Configuration or nil＃> URL：storeURL 
 options：options error： & error]）{
 //处理错误。 
} 
  

我的 NSPersistentStoreCoordinator 以这种方式初始化：

   - （NSPersistentStoreCoordinator *）persistentStoreCoordinator {
 
 if（persistentStoreCoordinator！= nil ）{
 return persistentStoreCoordinator; 
} 
 
 NSURL * storeUrl = [NSURL fileURLWithPath：[[self applicationDocumentsDirectory] ​​stringByAppendingPathComponent：@FC.sqlite]]; 
 
 NSError * error = nil; 
 persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel：[self managedObjectModel]]; 
 if（！[persistentStoreCoordinator addPersistentStoreWithType：NSSQLiteStoreType configuration：nil URL：storeUrl options：nil error：& error]）{
 
 NSLog（@Unresolved error％@，％@ error，[error userInfo]）; 
 abort（）; 
} 
 
 return persistentStoreCoordinator; 
} 
  

我无法看到我应该如何添加苹果代码以获得自动轻量级迁移工作？

解决方案

这是我做了自动轻量级迁移： http://brainwashinc.wordpress.com/ 2010/01/18 / iphone-coredata-automatic-light-migration / ）

1。

将您的persistentStoreCoordinator创建更改为此（替换YOURDB）：

   - （NSPersistentStoreCoordinator *）persistentStoreCoordinator {
 
 if（persistentStoreCoordinator！= nil）{
 return persistentStoreCoordinator; 
} 
 
 NSURL * storeUrl = [NSURL fileURLWithPath：[[self applicationDocumentsDirectory] ​​stringByAppendingPathComponent：@YOURDB.sqlite]]; 
 
 // handle db upgrade 
 NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys：
 [NSNumber numberWithBool：YES]，NSMigratePersistentStoresAutomaticallyOption，
 [NSNumber numberWithBool：YES]，NSInferMappingModelAutomaticallyOption ，nil]; 
 
 NSError * error = nil; 
 persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel：[self managedObjectModel]]; 
 if（！[persistentStoreCoordinator addPersistentStoreWithType：NSSQLiteStoreType configuration：nil URL：storeUrl options：options error：& error]）{
 //处理错误
} 
 
 return persistentStoreCoordinator; 
} 
  

2。

选择您的xcdatamodel文件
设计 - >数据模型 - >添加模型版本（展开您的xcdatamodeld项目）
选择2（或更高版本）文件，设计 - >数据模型 - >设置当前版本（编辑此版本）

3。在应用程式委托中指定momd资源。

将您的managedObjectModel实作变更为这个（替换YOURDB）

   - （NSManagedObjectModel *）managedObjectModel {
 
 if（managedObjectModel！= nil）{
 return managedObjectModel; 
} 
 
 NSString * path = [[NSBundle mainBundle] pathForResource：@YOURDBofType：@momd]; 
 NSURL * momURL = [NSURL fileURLWithPath：path]; 
 managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL：momURL]; 
 
 return managedObjectModel; 
} 
  

I would like to make my app able to do an automatic lightweight migration when I add new attributes to my core data model.

In the guide from Apple this is the only info on the subject I could find:

Automatic Lightweight Migration

To request automatic lightweight migration, you set appropriate flags in the options dictionary you pass in addPersistentStoreWithType:configuration:URL:options:error:. You need to set values corresponding to both the NSMigratePersistentStoresAutomaticallyOption and the NSInferMappingModelAutomaticallyOption keys to YES:

NSError *error;
NSURL *storeURL = <#The URL of a persistent store#>;
NSPersistentStoreCoordinator *psc = <#The coordinator#>;
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
    [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
    [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

if (![psc addPersistentStoreWithType:<#Store type#>
    configuration:<#Configuration or nil#> URL:storeURL
    options:options error:&error]) {
    // Handle the error.
}

My NSPersistentStoreCoordinator is initialized in this way:

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }

    NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"FC.sqlite"]];

    NSError *error = nil;
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) {

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    

    return persistentStoreCoordinator;
}

I am having trouble seeing where and how I should add the Apple code to get the Automatic Lightweight Migration working?

解决方案

This is what I did to make Automatic Lightweight Migration (Source: http://brainwashinc.wordpress.com/2010/01/18/iphone-coredata-automatic-light-migration/)

1. Set the Persistent Store options for automatic migration in the app delegate.

Change your persistentStoreCoordinator creation to this (replace YOURDB):

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

  if (persistentStoreCoordinator != nil) {
    return persistentStoreCoordinator;
  }

  NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"YOURDB.sqlite"]];

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

  NSError *error = nil;
  persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
  if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) {
    // Handle error
  }

  return persistentStoreCoordinator;
}

2. Version your Data Model and Edit the new file.

Select your xcdatamodel file Design -> Data Model -> Add Model Version (expand your xcdatamodeld item) Select the "2″ (or later) file, Design -> Data Model -> Set Current Version (edit this version)

3. Specify the momd resource in app delegate.

Change your managedObjectModel implementation to this (replace YOURDB)

- (NSManagedObjectModel *)managedObjectModel {

  if (managedObjectModel != nil) {
    return managedObjectModel;
  }

  NSString *path = [[NSBundle mainBundle] pathForResource:@"YOURDB" ofType:@"momd"];
  NSURL *momURL = [NSURL fileURLWithPath:path];
  managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL];

  return managedObjectModel;
}

这篇关于“自动轻量级迁移”的实现核心数据（iPhone）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！