iphone - 如何在应用程序更新时保留现有数据库？

Question

我有一个 iPhone 应用程序，它使用 Sqlite 数据库来存储一些数据和一些用户配置。我遇到的问题是，当我提交应用程序的更新时，用户安装上的现有数据库将被空数据库覆盖，并且用户丢失了其配置。我确信避免这种情况不会太困难，但我不知道该怎么做。

这是我创建数据库副本的方法的代码:

// Creates a writable copy of the bundled default database in the application Documents directory.
- (void)createEditableCopyOfDatabaseIfNeeded {
    // First, test for existence.
    BOOL success;
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;
    NSString *writableDBPath = [self databasePath];
    success = [fileManager fileExistsAtPath:writableDBPath];
    if (!success) {
        // The writable database does not exist, so copy the default to the appropriate location.
        //NSLog(dbName);
        NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:dbName];
        success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
        if (!success) {
            NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);
        }
    }
}

这个方法称为表单:

- (BOOL)openDatabase {
    BOOL success = true;
    if (!database) {
        [self createEditableCopyOfDatabaseIfNeeded];
        if (sqlite3_open([[self databasePath] UTF8String], &database) != SQLITE_OK) {
            success = false;
            // Even though the open failed, call close to properly clean up resources.
            sqlite3_close(database);
            NSAssert1(0, @"Failed to open database with message '%s'.", sqlite3_errmsg(database));
        }
    }
    return success;
}


- (NSString*)databasePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:dbName];
    return path;
}

也许我忘记了代码中的某些内容？

有人可以帮我解决这个问题吗？谢谢你!

Answer 1

如何将 sqlite 数据库从主包复制到应用程序的文档目录，但前提是该数据库尚不存在？