Question

我有一个应用程序，其中PersistentStoreCoordinator在AppDelegate中设置。我想从已保存的sqlite文件列表中加载一个新的sqlite数据库。我很高兴删除现有的Persistent Store和sqlite文件，并将sqlite文件替换为从表中加载的文件。但是，如何从选择新文件的ViewController操作重新加载/刷新PersistentStoreCoordinator？我已经尝试将AppDelegate设置为ViewController的委托，但这似乎在应用程序中创建了各种循环引用。另外，重新加载PersistentStoreCoordinator的精确方法是什么？

我已经尝试过这段代码，但它只是清除了持久存储而没有使用加载的sqlite文件刷新（Working.sqlite是当前正在运行的sqlite数据库版本的名称）：

 -  (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
        NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
        targetPath = [libraryPath stringByAppendingPathComponent:@"Working.sqlite"]; 
AppDelegate *delegate = [[UIApplication sharedApplication] delegate];

        NSPersistentStore *store = [[delegate.persistentStoreCoordinator persistentStores] lastObject];
        NSError *error;

        NSPersistentStoreCoordinator *storeCoordinator = delegate.persistentStoreCoordinator;
        [storeCoordinator removePersistentStore:store error:&error];
        [[NSFileManager defaultManager] removeItemAtPath:targetPath error:&error];


        NSString *loadPath = [workingDirPath stringByAppendingPathComponent:[directoryContent objectAtIndex:indexPath.row]];
        NSString *loadName = [[directoryContent objectAtIndex:indexPath.row] stringByDeletingPathExtension];
        NSLog(@"selectedPlan is: %@", loadName);


        if (![[NSFileManager defaultManager] copyItemAtPath:loadPath toPath:targetPath error:&error]) {
            NSLog(@"Error: %@", error);
        }



        else {
            [delegate managedObjectContext];
            [delegate managedObjectModel];
            [delegate persistentStoreCoordinator];
           [self.delegate planWasSelectedOnTheFileTableViewController:self];}

好的 - 我现在已经修改了下面的代码，当我选择要加载的行时，当我最后将新商店添加到PSC时，我现在遇到了崩溃。错误代码都是null，所以我不确定什么是失败的。 NSLogs显示原始商店已被删除，新版本已复制。

-  (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
    targetPath = [libraryPath stringByAppendingPathComponent:@"Working.sqlite"]; AppDelegate *delegate = [[UIApplication sharedApplication] delegate];

    NSPersistentStore *store = [[delegate.persistentStoreCoordinator persistentStores] lastObject];
    NSError *error;

    NSString *loadPath = [workingDirPath stringByAppendingPathComponent:[directoryContent objectAtIndex:indexPath.row]];
    NSString *loadName = [[directoryContent objectAtIndex:indexPath.row] stringByDeletingPathExtension];
    NSLog(@"selectedPlan is: %@", loadName);
    [delegate.persistentStoreCoordinator removePersistentStore:store error:&error];
    [[NSFileManager defaultManager] removeItemAtPath:targetPath error:&error];

    if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"It's still there!");

    }
    else {NSLog(@"File deleted");}
    [[NSFileManager defaultManager] copyItemAtPath:loadPath toPath:targetPath error:&error];
    if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"File Copied");

    }
    else {NSLog(@"path empty");}
    NSURL *storeURL = [NSURL fileURLWithPath:targetPath];
        error = nil;
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

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

       [self.delegate planWasSelectedOnTheFileTableViewController:self];}

Marcus - 我认为这反映了您的建议，但我仍然会在addPersistentStore阶段使用“未解决的错误”日志崩溃：

-  (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    AppDelegate *delegate = [[UIApplication sharedApplication] delegate];

    //setting path to current working sqlite file
    NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
    targetPath = [libraryPath stringByAppendingPathComponent:@"Working.sqlite"];

    //setting path to selected sqlite file
    NSString *loadPath = [workingDirPath stringByAppendingPathComponent:[directoryContent objectAtIndex:indexPath.row]];
    NSString *loadName = [[directoryContent objectAtIndex:indexPath.row] stringByDeletingPathExtension];
    NSLog(@"selectedPlan is: %@", loadName);

    // retrieve the store URL
    NSURL * storeURL = [NSURL fileURLWithPath:targetPath];
    NSString *storeName = [storeURL absoluteString];
     NSLog(@"Persistent Store is: %@", storeName);
    if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"It was there before it was deleted");}

    // remove the store
    NSError *error;
    [delegate.persistentStoreCoordinator removePersistentStore:[[delegate.persistentStoreCoordinator persistentStores] lastObject] error:&error];
{NSLog(@"Unresolved error on remove %@, %@", error, [error userInfo]);
    abort();}
error = nil;


    // remove the store file and check it's gone
    [[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error];
    if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"It's still there!");}
        else {NSLog(@"File deleted");}

    // copy in new file and check it's there
    [[NSFileManager defaultManager] copyItemAtPath:loadPath toPath:targetPath error:&error];
        if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"File Copied");}
        else {NSLog(@"path empty");}

    //re-attach the store
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                             [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

    [delegate.persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error];
    {NSLog(@"Unresolved error on add %@, %@", error, [error userInfo]);
        abort();}
 }

根据Marcus的建议，我在上面修改过的代码中添加了removePersistentStore上的错误日志。删除操作中会出现此问题。日志文件的结尾如下：

2013-06-01 01：10：02.478 inControl [1238：907] Persistent Store是：file：//localhost/var/mobile/Applications/D34C6065-8D59-480F-ABA4-9F10C690F26C/Library/Working.sqlite

2013-06-01 01：10：02.481 inControl [1238：907]它被删除之前就已存在

2013-06-01 01：10：02.486 inControl [1238：907]删除时未解决的错误（null），（null）

根据Marcus的建议最终工作代码：

-  (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    AppDelegate *delegate = [[UIApplication sharedApplication] delegate];

    //setting path to current working sqlite file
    NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
    targetPath = [libraryPath stringByAppendingPathComponent:@"Working.sqlite"];

    //setting path to selected sqlite file
    NSString *loadPath = [workingDirPath stringByAppendingPathComponent:[directoryContent objectAtIndex:indexPath.row]];
    NSString *loadName = [[directoryContent objectAtIndex:indexPath.row] stringByDeletingPathExtension];
    NSLog(@"selectedPlan is: %@", loadName);

    // retrieve the store URL
    NSURL * storeURL = [NSURL fileURLWithPath:targetPath];
    NSString *storeName = [storeURL absoluteString];
     NSLog(@"Persistent Store is: %@", storeName);
    if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"It was there before it was deleted");}

    // remove the store
    NSError *error;
    NSPersistentStoreCoordinator *psc = [delegate persistentStoreCoordinator];
    NSPersistentStore *ps = [[psc persistentStores] lastObject];
    if (![psc removePersistentStore:ps error:&error]) {
        NSLog(@"Remove Store Failure: %@\n%@", [error localizedDescription], [error userInfo]);
        abort();
    }    error = nil;

    // remove the store file and check it's gone
    [[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error];


    if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"It's still there!");}
        else {NSLog(@"File deleted");}

    // copy in new file and check it's there
    [[NSFileManager defaultManager] copyItemAtPath:loadPath toPath:targetPath error:&error];
        if ([[NSFileManager defaultManager] fileExistsAtPath:targetPath]){NSLog(@"File Copied");}
        else {NSLog(@"path empty");}

    [delegate.managedObjectContext reset];
    //re-attach the store
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                             [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                             [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

    if (![psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {
        NSLog(@"Add Store Failure: %@\n%@", [error localizedDescription], [error userInfo]);
        abort();
    }
    }

Answer 1

最佳答案是在-removePersistentStore:error:上执行NSPersistentStoreCoordinator然后执行-addPersistentStoreWithType: configuration: configuration URL: options: error:

作为该过程的一部分，我会在-reset上执行NSManagedObjectContext，然后发布您的视图控制器正在侦听的NSNotification，然后您的视图控制器就可以重新加载其数据。

您无需从磁盘中删除任何文件。

更新1

首先，您需要告诉我们崩溃是什么：）

其次，您没有在-removePersistentStore...上使用错误参数，因此您可能会在那里收到错误。

使用崩溃更新问题，这将有助于对此进行排序。

更新2

这段代码没有任何意义：

// remove the store
NSError *error;
[delegate.persistentStoreCoordinator removePersistentStore:[[delegate.persistentStoreCoordinator persistentStores] lastObject] error:&error];
{NSLog(@"Unresolved error on remove %@, %@", error, [error userInfo]);
abort();}
error = nil;

如果这是准确的，那就错了。它应该是：

NSError *error;
NSPersistentStoreCoordinator *psc = [delegate persistentStoreCoordinator];
NSPersistentStore *ps = [[psc persistentStores] lastObject];
if (![psc removePersistentStore:ps error:&error]) {
  NSLog(@"Failure: %@\n%@", [error localizedDescription], [error userInfo]);
  abort();
}

请勿回复错误以确定失败，请检查通话中返回的BOOL。

从ViewController刷新AppDelegate中的NSPersistentStoreCoordinator

1 个答案:

更新1

更新2