ios - 如何重新创建 persistentStore 不受更改 .xcdatamodeld 的影响

Question

我想重新创建(删除并创建)persistentStore，使其不受更改 .xcdatamodeld 的影响。

我在 AppDelegate 中写了一段代码 persistentStoreCoordinator，如下所示:

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

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

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

    // delete if database exists
    NSError *error = nil;
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

        // if .xcdatamodeld is changed, fail and in here...
        // if not changed, recreate success. all data removed from database

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    NSArray *stores = [_persistentStoreCoordinator persistentStores];
    for (NSPersistentStore *store in stores) {
        [_persistentStoreCoordinator removePersistentStore:store error:nil];
        [[NSFileManager defaultManager] removeItemAtPath:store.URL.path error:nil];
    }

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

    return _persistentStoreCoordinator;
}

当我对 .xcdatamodeld 进行更改(例如，向实体添加新列)并重新启动模拟器时，然后首先失败 addPersistentStoreWithType 并且日志显示

Unresolved error Error Domain=NSCocoaErrorDomain Code=134100 
The operation couldn’t be completed. (Cocoa error 134100.)

我该怎么做？

Answer 1

下面的代码对我来说似乎工作得很好。

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

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

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

    // delete database if exists
    [[NSFileManager defaultManager] removeItemAtPath:storeURL.path error:nil];

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

    return _persistentStoreCoordinator;
}

我在下面检查(在设备和模拟器中):

1. 首次启动时，应创建数据库
2. 编辑 .xcdatamodeld(添加/编辑/删除列或实体)然后重新启动，应重新创建数据库

感谢您的建议。