Question

我正在尝试使用Struct来传递我从Facebook图形请求中获得的一些变量，例如电子邮件，姓名，性别等。我在'ViewController'中创建了Struct（'fbDemographics'）和变量，但是当我尝试调用struct并且'SecondViewController'中的一个变量时，我得到一个错误（Type'ViewController'没有成员'fbDemographics' ）。我之前从未使用过struct，所以有点困惑为什么我会收到这个错误。谢谢你的任何想法。两个视图控制器的代码如下：

class ViewController: UIViewController, FBSDKLoginButtonDelegate {

override func viewDidLoad() {
    super.viewDidLoad()

    struct fbDemographics {

        static var relationship_status: String?
        static var gender: String?
        static var user_education_history: String?
        static var user_location: String?
        static var email: String?
        static var name: String?

    }     

    FBSDKGraphRequest(graphPath: "me", parameters: ["fields": "id, name, relationship_status, gender, user_location, user_education_history, email"]).start(completionHandler: { (connection, result, error) -> Void in
        if (error == nil){
            //let fbDetails = result as! NSDictionary
            //print(fbDetails)

            if let userDataDict = result as? NSDictionary {
                fbDemographics.gender = userDataDict["gender"] as? String
                fbDemographics.email = userDataDict["email"] as? String
                fbDemographics.name = userDataDict["name"] as? String
                fbDemographics.user_location = userDataDict["user_location"] as? String
                fbDemographics.user_education_history = userDataDict["user_education_history"] as? String
                fbDemographics.relationship_status = userDataDict["relationship_status"] as? String


                let myEducation = fbDemographics.user_education_history
                let myEmail = fbDemographics.email
                let myGender = fbDemographics.gender
                let myName = fbDemographics.name
                let myStatus = fbDemographics.relationship_status
                let myLocation = fbDemographics.user_location                   

                self.performSegue(withIdentifier: "LoginToHome", sender: (Any).self)


            }


        }

第二视图控制器

class SecondViewController: UIViewController {

@IBAction func verticalSliderChanged(_ sender: UISlider) {

        let currentValue = String(sender.value);

        sliderLabel.text = "\(currentValue)"

    func viewDidLoad() {
        super.viewDidLoad()

        ***ViewController.fbDemographics.myEmail***

    }
}

Answer 1

问题在于您已在 struct内定义了viewDidLoad 。因此范围仅限于该方法。将其移出viewDidLoad，但仍在ViewController，您应该可以从SecondViewController访问它。显然，您也必须修改对myEmail的引用，因为它被称为email。此外，在您的SecondViewController中，您应该将viewDidLoad实施从verticalSliderChanged方法中拉出来; viewDidLoad应该是SecondViewController的顶级实例方法，未在另一个方法中定义。

但这里存在更深层次的问题。您应该制作这些简单的实例变量，而不是将struct与static变量一起使用，创建FbDemographics类型的实例（注意，使用大写字母开始struct类型），然后在prepare(for:sender:)中传递此实例。

例如，传递数据的正确方法是：

消除static个变量;

给你的struct一个以大写字母开头的名字;

创建struct的实例;和

将此实例传递到prepare(for:sender:)中的目标视图控制器。

E.g。

struct FbDemographics { var relationshipStatus: String? var gender: String? var userEducationHistory: String? var userLocation: String? var email: String? var name: String? } class ViewController: UIViewController { var demographics: FbDemographics? override func viewDidLoad() { super.viewDidLoad() performRequest() // I actually don't think you should be initiating this in `viewDidLoad` ... perhaps in `viewDidAppear` } override func prepare(for segue: UIStoryboardSegue, sender: Any?) { if let destination = segue.destination as? SecondViewController { destination.demographics = demographics } } func performRequest() { FBSDKGraphRequest(graphPath: "me", parameters: ["fields": "id, name, relationship_status, gender, user_location, user_education_history, email"]).start { connection, result, error in guard let userDataDict = result as? NSDictionary, error == nil else { print("\(error)") return } self.demographics = FbDemographics( relationshipStatus: userDataDict["relationship_status"] as? String, gender: userDataDict["gender"] as? String, userEducationHistory: userDataDict["user_education_history"] as? String, userLocation: userDataDict["user_location"] as? String, email: userDataDict["email"] as? String, name: userDataDict["name"] as? String ) self.performSegue(withIdentifier: "LoginToHome", sender: self) } } }

然后SecondViewController可以：

class SecondViewController: UIViewController { var demographics: FbDemographics! override func viewDidLoad() { super.viewDidLoad() let value = demographics.email // this should work fine here } }

使用Struct传递变量Swift

1 个答案: