在 Swift 中复制 Sqlite 数据库无法正常工作答案

【问题标题】：Copy Sqlite DataBase in Swift does not work properly在 Swift 中复制 Sqlite 数据库无法正常工作
【发布时间】：2017-01-10 07:50:47
【问题描述】：

我正在为目标 c 使用以下代码来复制 sqlite 数据库，它工作正常。但是当我将此代码转换为 swift 时，它会在 Bool 类型上显示错误。

这是目标c代码

  - (void) copyDatabaseIfNeeded {

  //Using NSFileManager we can perform many file system operations.
   NSFileManager *fileManager = [NSFileManager defaultManager];
   NSError *error;

   NSString *dbPath = [self getDBPath];
   BOOL success = [fileManager fileExistsAtPath:dbPath];

  if(!success) {

   NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"database.sqlite"];
   success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error];

   if (!success)
      NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);
   }
   }

  - (NSString *) getDBPath
  {   

   NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
   NSString *documentsDir = [paths objectAtIndex:0];
   return [documentsDir   stringByAppendingPathComponent:@"database.sqlite"];
  }

这是导致问题的 Swift 的 CopyDataBase。

   var fileManager = FileManager.default
   var error: Error!
   var dbPath = self.getDBPath()
   var success = fileManager.fileExists(atPath: dbPath)
   if !success {
   var defaultDBPath = URL(fileURLWithPath: Bundle.main.resourcePath!).appendingPathComponent("CapalinoDataBase.sqlite").absoluteString
   do {
    success = try fileManager.copyItem(atPath: defaultDBPath, toPath: dbPath)
    }
    catch {
    }
    if !success {
    assert(false, "Failed to create writable database file with message '\(error.localizedDescription)'.")
    }
      }

【问题讨论】：

标签： ios objective-c sqlite swift3

【解决方案1】：

请试试这个。

func copyDatabse() {

        let fileMgr = FileManager.default

        if let path = Bundle.main.path(forResource: "db", ofType:"sqlite") {

            do {
                try fileMgr.copyItem(atPath: path, toPath: dbPath())
                print("Copy success")
            }
            catch {
                print(error.localizedDescription )
            }
        }
    }


    func dbPath() -> String {

        let dirPaths =  NSSearchPathForDirectoriesInDomains(.documentDirectory,.userDomainMask, true)
        let docsDir = dirPaths[0]

        let destPath = (docsDir as NSString).appendingPathComponent("/db.sqlite")

        return destPath
    }

【讨论】：

【解决方案2】：

在 swift 中使用单吨类使用 SQLIte 的最佳方式。

Download example

func methodToCreateDatabase() -> NSURL? {

    let fileManager = NSFileManager.defaultManager()

    let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)

    if let documentDirectory:NSURL = urls.first { // No use of as? NSURL because let urls returns array of NSURL

        // exclude cloud backup
        do {
            try documentDirectory.setResourceValue(true, forKey: NSURLIsExcludedFromBackupKey)
        } catch _{
            print("Failed to exclude backup")
        }

        // This is where the database should be in the documents directory
        let finalDatabaseURL = documentDirectory.URLByAppendingPathComponent("contact.db")

        if finalDatabaseURL.checkResourceIsReachableAndReturnError(nil) {
            // The file already exists, so just return the URL
            return finalDatabaseURL
        } else {
            // Copy the initial file from the application bundle to the documents directory
            if let bundleURL = NSBundle.mainBundle().URLForResource("contact", withExtension: "db") {

                do {
                    try fileManager.copyItemAtURL(bundleURL, toURL: finalDatabaseURL)
                } catch _ {
                    print("Couldn't copy file to final location!")
                }

            } else {
                print("Couldn't find initial database in the bundle!")
            }
        }
    } else {
        print("Couldn't get documents directory!")
    }

    return nil
}

【讨论】：

【解决方案3】：

Please try this one it is working on swift 3.0

func copyDatabaseIfNeeded() {
    //Using NSFileManager we can perform many file system operations.
    let fileManager = FileManager.default
    let error: Error?
    let dbPath: String = self.getDBPath()
    var success: Bool = fileManager.fileExists(atPath: dbPath)
    if !success {
        let defaultDBPath: String = URL(fileURLWithPath: (Bundle.main.resourcePath)!).appendingPathComponent("database.sqlite").absoluteString

        do {
            success = try fileManager.copyItem(atPath: defaultDBPath, toPath: dbPath) as Any as! Bool
        }
        catch let error as NSError {
            print("Ooops! Something went wrong: \(error)")
        }

        if !success {
            assert(false, "Failed to create writable database file with message '\(error?.localizedDescription)'.")
        }
    }
}

func getDBPath() -> String {
    let paths: [Any] = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
    let documentsDir: String = paths[0] as! String
    return URL(fileURLWithPath: documentsDir).appendingPathComponent("database.sqlite").absoluteString
}

【讨论】：