如何使用從iCloud下載的另一個領域替換默認領域

Question

我的應用使用CloudKit備份領域數據並在用戶按某個按鈕時獲取數據。 我使用下面的代碼將文件夾中的「default.realm」文件上傳到iCloud。 而數據似乎上傳得很好。

// create file path from app's documents folder 
NSString* filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
NSString* fileName = @"default.realm"; 
NSString* fileAtPath = [filePath stringByAppendingPathComponent:fileName]; 
CKRecordID *recordID = [[CKRecordID alloc] initWithRecordName:kRecordName]; 
CKRecord *record = [[CKRecord alloc] initWithRecordType:kRecordType recordID:recordID]; 

if ([[NSFileManager defaultManager] fileExistsAtPath:fileAtPath]) { 
    CKAsset *asset = [[CKAsset alloc] initWithFileURL:[NSURL fileURLWithPath:fileAtPath]]; 
    [record setObject:asset forKey:@"Realm"]; 
} 

// upload 
CKDatabase *privateDatabase = [[CKContainer defaultContainer] privateCloudDatabase]; 
[privateDatabase saveRecord:record completionHandler:^(CKRecord *record, NSError *error) { 
    // completion handling 
} 

下面是下載部分。我也可以下載，但似乎領域文件沒有被替換。

CKDatabase *privateDatabase = [[CKContainer defaultContainer] privateCloudDatabase]; 
CKRecordID *recordID = [[CKRecordID alloc] initWithRecordName:kRecordName]; 

// fetch realm from cloud 
[privateDatabase fetchRecordWithID:recordID completionHandler:^(CKRecord *record, NSError *error) { 
    if (!error) { 
     CKAsset *realmAsset = record[@"Realm"]; 
     NSData *realmData = [NSData dataWithContentsOfURL:realmAsset.fileURL]; 
     NSString* filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
     NSString* fileName = @"default.realm"; 
     NSString* fileAtPath = [filePath stringByAppendingPathComponent:fileName]; 

     // delete existing default.realm file in documents 
     if ([[NSFileManager defaultManager] fileExistsAtPath:fileAtPath]) { 
      [[NSFileManager defaultManager] removeItemAtPath:fileAtPath error:&error]; 
     } 
     // create a new default.realm file with downloaded data 
     if([[NSFileManager defaultManager] createFileAtPath:fileAtPath contents:realmData attributes:nil]) { 
       // code goes thru here but nothing changes 
     } 
    } 
}]; 

我想替換整個領域文件。我究竟做錯了什麼？我應該從哪裏開始？ 任何意見將不勝感激。

Answer 1

要更改Realm文件路徑，請將路徑設置爲Realm.Configuration.fileURL。

let fileURL = ... 
let config = Realm.Configuration(fileURL: fileURL) 

let realm = try! Realm(configuration: config) 

如果您不想每次都指定文件路徑，可以將配置對象設置爲默認配置。

let fileURL = ... 
let config = Realm.Configuration(fileURL: fileURL) 

Realm.Configuration.defaultConfiguration = config 

let realm = try! Realm() 

也https://realm.io/docs/swift/latest/#realm-configuration

見在此基礎上，在運行時交換的文件境界是非常危險的。要做到這一點，你必須保證沒有Realm的強大參考。除此之外，您可以創建另一個文件並切換到使用它。

// fetch realm from cloud 
[privateDatabase fetchRecordWithID:recordID completionHandler:^(CKRecord *record, NSError *error) { 
    if (!error) { 
     CKAsset *realmAsset = record[@"Realm"]; 
     ... 

     // Do not delete existing default.realm file in documents 

     // create a new default.realm file with downloaded data 
     // as deferent file name 

     NSString* newFileName = @"default1.realm"; // default2.realm, default3.realm, ... 
     NSString* newfileAtPath = [filePath stringByAppendingPathComponent:newfileAtPath]; 
     if([[NSFileManager defaultManager] createFileAtPath:newfileAtPath contents:realmData attributes:nil]) { 
       // Switch to using new file to create Realm instance 
       // e.g. set new file path to de default configuration file URL 
       let config = Realm.Configuration(fileURL: NSURL(fileURLWithPath: newfileAtPath)!) 
       Realm.Configuration.defaultConfiguration = config 
       ... 
     }