无法将类型“（）”的值转换为预期的参数类型“字符串”

Posted 2023-03-05

【中文标题】无法将类型“（）”的值转换为预期的参数类型“字符串”

【英文标题】：Cannot convert value of type '()' to expected argument type 'String'

【发布时间】：2018-01-05 03:52:34

【问题描述】：

我正在获取用户输入的邮政编码并将其转换为城市名称。将其转换为城市名称后，我会将信息保存到我的 Firebase 数据库中。当我尝试执行此操作时，出现错误“无法将 '()' 类型的值转换为预期的参数类型 'String'”。我从文本字段中获取邮政编码并从以前的 ViewController 传递它。 error

 //first ViewController


 override func prepare(for segue: UIStoryboardSegue, sender: Any?)



    if let destination = segue.destination as? SignUpSecondViewController

    destination.zipCode = zipCodeInput.text! 
    destination.name = nameText.text!
    destination.email = emailText.text!
    destination.password = passwordText.text!
    destination.pictureData = userImageView.image!
    



   //second ViewController

    var zipCode = String()

 func getLocationFromPostalCode(postalCode : String)
    let geocoder = CLGeocoder()

    geocoder.geocodeAddressString(postalCode) 
        (placemarks, error) -> Void in
        // Placemarks is an optional array of type CLPlacemarks, first item in array is best guess of Address

        if let placemark = placemarks?[0] 

            if placemark.postalCode == postalCode
                // you can get all the details of place here
                print("\(placemark.locality)")
                print("\(placemark.country)")
            
            else
                print("Please enter valid zipcode")
            
        
    





 @IBAction func completeButtonAction(_ sender: Any) 

let nameText = name
let emailField = email.lowercased()
let finalEmail = emailField.trimmingCharacters(in: .whitespacesAndNewlines)
let location = getLocationFromPostalCode(postalCode: zipCode)
let biography = bioTextView.text!
let passwordText = password
let interests = options.joined(separator: " , ")

    var pictureD: NSData?


    if let imageView = self.sentPic.image 
        pictureD = UIImageJPEGRepresentation(self.sentPic.image!, 0.70) as! NSData
    


    if  finalEmail.isEmpty || biography.isEmpty || password.isEmpty || pictureD == nil 
        self.view.endEditing(true)
        let alertController = UIAlertController(title: "OOPS", message: " You must fill all the fields", preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
        present(alertController, animated: true, completion: nil)

    else 
        SVProgressHUD.show()

        self.view.endEditing(true)
        authService.signUP(firstLastName: nameText, email: finalEmail, location: location, biography: biography, password: password, interests: interests, pictureData: pictureD as NSData!)

    
    SVProgressHUD.dismiss()


    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let vc = storyboard.instantiateViewController(withIdentifier: "NewTabBarViewController") as! UIViewController
    // Alternative way to present the new view controller
     self.navigationController?.present(vc, animated: true, completion: nil)

【问题讨论】：

先解决let location = getLocationFromPostalCode(postalCode: zipCode)的问题。这绝对是错误的。

nameText 是你的文本字段吗？

如何解决问题以从该函数获取输出？

nameText 是一个不同的输入，zipCode 文本字段用于邮政编码，我正在尝试将其转换为位置属性的城市名称后保存

你必须在getLocationFromPostalCode中返回一个字符串。

【参考方案1】：

你的问题从这行开始：

let location = getLocationFromPostalCode(postalCode: zipCode)

问题是你的getLocationFromPostalCode没有返回值，所以编译器认为location的隐式类型是()，这意味着一个没有返回（void）类型的函数。

所以，理论上，你会想要改变：

func getLocationFromPostalCode(postalCode : String) 

到：

func getLocationFromPostalCode(postalCode : String) -> String 

并让函数返回一个String 值。

但是，您也不能这样做，因为您的 getLocationFromPostalCode 的实现包括从异步网络调用中获取位置。

正确的解决方案是重写该函数以采用返回获得的位置的完成处理程序。

func getLocationFromPostalCode(postalCode: String, completion: (String?) -> Void) 
    let geocoder = CLGeocoder()

    geocoder.geocodeAddressString(postalCode)  (placemarks, error) -> Void in
        // Placemarks is an optional array of type CLPlacemarks, first item in array is best guess of Address

        if let placemark = placemarks?.first 
            if placemark.postalCode == postalCode 
                // you can get all the details of place here
                print("\(placemark.locality)")
                print("\(placemark.country)")
                completion(placemark.locality) // or whatever value you want
                return
            
            else
                print("Please enter valid zipcode")
            
        

        completion(nil) // no location found
    

现在，一切都搞定了，你需要重做获取位置的方法。

@IBAction func completeButtonAction(_ sender: Any) 
    var pictureD: Data? = nil
    if let imageView = self.sentPic.image 
        pictureD = UIImageJPEGRepresentation(imageView, 0.70)
    

    let emailField = email.lowercased()
    let finalEmail = emailField.trimmingCharacters(in: .whitespacesAndNewlines)
    let biography = bioTextView.text!
    let passwordText = password

    if  finalEmail.isEmpty || biography.isEmpty || password.isEmpty || pictureD == nil 
        self.view.endEditing(true)
        let alertController = UIAlertController(title: "OOPS", message: " You must fill all the fields", preferredStyle: .alert)
        alertController.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
        present(alertController, animated: true, completion: nil)
    else 
        getLocationFromPostalCode(postalCode: zipCode)  (location) in
            guard let location = location else 
                print("no location")
                return
            

            let nameText = name
            let interests = options.joined(separator: " , ")

            SVProgressHUD.show()

            self.view.endEditing(true)
            authService.signUP(firstLastName: nameText, email: finalEmail, location: location, biography: biography, password: password, interests: interests, pictureData: pictureD!)
            SVProgressHUD.dismiss()
        
    

    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let vc = storyboard.instantiateViewController(withIdentifier: "NewTabBarViewController") as! UIViewController
    // Alternative way to present the new view controller
    self.navigationController?.present(vc, animated: true, completion: nil)