在iOS 7中预加载数据库 [英] Preloading a database in iOS 7

问题描述

在过去，我已经释放了我的应用程序与预加载的数据库，所以用户不必在第一次运行时更新它。有一些代码我发现在另一个问题SO（对不起，没有链接了），我添加到我的应用程序代表的 persistentStoreCoordinator 方法：

In the past I have released my app with a database that was preloaded, so the user didn't have to update it on the first run. There was some code I found in another question on SO (sorry, don't have the link anymore) that I added to my App Delegate's persistentStoreCoordinator method:

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"db.sqlite"];
    if (![[NSFileManager defaultManager] fileExistsAtPath:[storeURL path]])
    {
        NSURL *preloadURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"db" ofType:@"sqlite"]];
        NSError* err = nil;

        if (![[NSFileManager defaultManager] copyItemAtURL:preloadURL toURL:storeURL error:&err])
        {
            NSLog (@"Error - Could not preload database.");
        }
    }

//... more code generated from the template here
}

当我尝试在iOS 7中这样做，我没有得到任何错误，但数据库是空的（即使数据库在我的 mainBundle 有我所期望的所有信息）。我注意到在 applicationDocumentsDirectory 中有更多的数据库文件（一个.sqlite-shm文件和一个.sqlite-wal文件）。我还需要对这些文件做一些事情吗？或者，它不再可能有一个预装载的数据库与应用程序？

When I try to do this in iOS 7, I don't get any errors, but the database is empty (even though the database in my mainBundle has all the info I'm expecting). I noticed that there are more database files (a .sqlite-shm file and a .sqlite-wal file) in the applicationDocumentsDirectory. Do I need to do something with those files as well? Or is it no longer possible to have a preloaded database ship with the app?

编辑：我尝试添加代码复制新的.sqlite-shm和.sqlite-wal

I tried adding code to copy the new .sqlite-shm and .sqlite-wal files as well, but that doesn't help.

推荐答案

核心数据在iOS 7中有所改变，主要是如何保存

Core Data has changed a bit in iOS 7, mainly how saves are performed.

写入日志（wal）是为了提高性能而引入的，因此您看到的WAL sqlite文件。

Write Ahead Logging (wal) was introduced to improve performance, hence the WAL sqlite file you see.

您可以告诉您的应用程序使用旧的日志模式：

You can tell your app to use the old 'journal mode':

您可以通过添加NSSQLitePragmasOption
调用
时的选项addPersistentStoreWithType：configuration：url：options：error。例如。 to
设置先前的默认模式DELETE：

You can specify the journal mode by adding the NSSQLitePragmasOption to the options when calling addPersistentStoreWithType:configuration:url:options:error. E.g. to set the previous default mode of DELETE:

NSDictionary *options = @{ NSSQLitePragmasOption : @{@"journal_mode" : @"DELETE"} };

来源

我不知道这是否会解决您的问题，但它是iOS 7中的核心数据发生了重大变化

I am not sure if this will fix your issue, but it is the big thing that has changed with Core Data in iOS 7

如果您想了解有关WAL的更多信息，建议您观看 WWDC会议＃207，Core Data& iCloud中的新功能

If you want to learn more about WAL, I suggest watching WWDC session #207, "Whats New In Core Data & iCloud"

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