在 Swift 中复制 Sqlite 数据库无法正常工作

Posted 2023-03-14

【中文标题】在 Swift 中复制 Sqlite 数据库无法正常工作

【英文标题】：Copy Sqlite DataBase in Swift does not work properly

【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)'.")
    
      

【参考方案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
    

【参考方案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

【参考方案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