我想为我的应用程序用户提供创建核心数据数据库备份的可能性，尤其是在他切换到新设备等情况下。
我该怎么做？特别是如何重新导入该文件？我的意思是，假设他制作了数据库的备份副本，然后更改了很多内容并想重置为先前保存的备份副本。我该怎么做？
谢谢!
最佳答案
让我们看一下这个示例应用程序，它包含用于进行备份，在iCloud之间复制备份以及从iCloud复制备份，通过电子邮件发送备份以及从电子邮件导入备份的功能。
http://ossh.com.au/design-and-technology/software-development/sample-library-style-ios-core-data-app-with-icloud-integration/
顺便说一句，如果您要与ICloud之间进行备份，则使用migrationPersistentStore API进行备份/导入要安全得多。另请注意，示例应用程序假定您未使用WAL模式，这是iOS 7的默认模式。WAL模式使用多个文件，所有这些文件都需要备份或复制。
以下是视频的链接，该视频演示了示例Apps备份和还原功能。
http://ossh.com.au/design-and-technology/software-development/sample-library-style-ios-core-data-app-with-icloud-integration/sample-apps-explanations/backup-files/
以下是用于创建备份副本的方法。请注意，可以使用多个persistentStoreCoordinators打开存储，因此在进行备份时无需将其关闭。还原它显然确实需要先删除现有存储。请注意，以下两种方法之间几乎没有什么区别，除了使用或不使用iCloud选项打开源存储。
/*! Creates a backup of the ICloud store
@return Returns YES of file was migrated or NO if not.
*/
- (bool)backupICloudStore {
FLOG(@"backupICloudStore called");
// Lets use the existing PSC
NSPersistentStoreCoordinator *migrationPSC = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];
// Open the store
id sourceStore = [migrationPSC addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[self icloudStoreURL] options:[self icloudStoreOptions] error:nil];
if (!sourceStore) {
FLOG(@" failed to add old store");
migrationPSC = nil;
return FALSE;
} else {
FLOG(@" Successfully added store to migrate");
NSError *error;
FLOG(@" About to migrate the store...");
id migrationSuccess = [migrationPSC migratePersistentStore:sourceStore toURL:[self backupStoreURL] options:[self localStoreOptions] withType:NSSQLiteStoreType error:&error];
if (migrationSuccess) {
FLOG(@"store successfully backed up");
migrationPSC = nil;
// Now reset the backup preference
[[NSUserDefaults standardUserDefaults] setBool:NO forKey:_makeBackupPreferenceKey];
[[NSUserDefaults standardUserDefaults] synchronize];
return TRUE;
}
else {
FLOG(@"Failed to backup store: %@, %@", error, error.userInfo);
migrationPSC = nil;
return FALSE;
}
}
migrationPSC = nil;
return FALSE;
}
/*! Creates a backup of the Local store
@return Returns YES of file was migrated or NO if not.
*/
- (bool)backupLocalStore {
FLOG(@"backupLocalStore called");
// Lets use the existing PSC
NSPersistentStoreCoordinator *migrationPSC = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];
// Open the store
id sourceStore = [migrationPSC addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[self localStoreURL] options:[self localStoreOptions] error:nil];
if (!sourceStore) {
FLOG(@" failed to add old store");
migrationPSC = nil;
return FALSE;
} else {
FLOG(@" Successfully added store to migrate");
NSError *error;
FLOG(@" About to migrate the store...");
id migrationSuccess = [migrationPSC migratePersistentStore:sourceStore toURL:[self backupStoreURL] options:[self localStoreOptions] withType:NSSQLiteStoreType error:&error];
if (migrationSuccess) {
FLOG(@"store successfully backed up");
migrationPSC = nil;
// Now reset the backup preference
[[NSUserDefaults standardUserDefaults] setBool:NO forKey:_makeBackupPreferenceKey];
[[NSUserDefaults standardUserDefaults] synchronize];
return TRUE;
}
else {
FLOG(@"Failed to backup store: %@, %@", error, error.userInfo);
migrationPSC = nil;
return FALSE;
}
}
migrationPSC = nil;
return FALSE;
}
/** Sets the selected file as the current store.
Creates a backup of the current store first.
@param fileURL The URL for the file to use.
*/
- (BOOL)restoreFile:(NSURL *)fileURL {
FLOG(@" called");
// Check if we are using iCloud
if (_isCloudEnabled) {
FLOG(@" using iCloud store so OK to restore");
NSURL *currentURL = [self storeURL];
FLOG(@" currentURL is %@", currentURL);
FLOG(@" URL to use is %@", fileURL);
[self saveContext];
[self backupCurrentStoreWithNoCheck];
// Close the current store and delete it
_persistentStoreCoordinator = nil;
_managedObjectContext = nil;
[self removeICloudStore];
[self moveStoreFileToICloud:fileURL delete:NO backup:NO];
} else {
FLOG(@" using local store so OK to restore");
NSURL *currentURL = [self storeURL];
FLOG(@" currentURL is %@", currentURL);
FLOG(@" URL to use is %@", fileURL);
[self saveContext];
[self backupCurrentStoreWithNoCheck];
// Close the current store and delete it
_persistentStoreCoordinator = nil;
_managedObjectContext = nil;
NSError *error = nil;
NSFileManager *fm = [[NSFileManager alloc] init];
// Delete the current store file
if ([fm fileExistsAtPath:[currentURL path]]) {
FLOG(@" target file exists");
if (![fm removeItemAtURL:currentURL error:&error]) {
FLOG(@" error unable to remove current store file");
NSLog(@"Error removing item Error: %@, %@", error, error.userInfo);
return FALSE;
} else {
FLOG(@" current store file removed");
}
}
//
//simply copy the file over
BOOL copySuccess = [fm copyItemAtPath:[fileURL path]
toPath:[currentURL path]
error:&error];
if (copySuccess) {
FLOG(@" replaced current store file successfully");
//[self postFileUpdateNotification];
} else {
FLOG(@"Error copying items Error: %@, %@", error, error.userInfo);
return FALSE;
}
}
// Now open the store again
[self openPersistentStore];
return TRUE;
}
关于iOS:如何创建核心数据库的备份副本？以及如何导出/导入该副本？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/22151650/