swift - 如何在另一个类中获取在一个类中声明的变量？

Question

我刚开始使用 Swift/firebase，抱歉我的笨拙。我正在使用 childbyautoid 将数据写入 firebase 数据库。我想访问另一个类中的最后一个键/ID。

    let postName = Database.database().reference().child("Event").childByAutoId()

    let postNameObject = [
        "EventName": NameTextField.text,
        "timestamp": [".sv":"timestamp"],
        "userID": Auth.auth().currentUser!.uid
    ] as [String:Any]

    postName.setValue(postNameObject, withCompletionBlock: { error, ref in
        if error == nil {
            self.dismiss(animated: true, completion: nil)
        } else {
        }
    })
    let childautoID = postName.key

我希望能够在另一个类中调用 childautoID 我们找到另一种方法来更新此节点。

Answer 1

您也许可以创建一个单例类来管理 Firebase 方法。每当使用 Firebase 构建应用程序时，我都会做类似的事情。这使您可以在多个类中全局引用值并使用与 Firebase 相关的方法。在我采用这种方法之前，我发现自己重写了相同的代码来将对象上传到 firebase。单例可让您创建可重复使用的代码，包括在此全局类中设置的“最后一个 key ”的存储。

class FirebaseManager {

    //You've probably seen something similar to this "shared" in other Apple frameworks
    //Maybe URLSession.shared or FileManager.default or UserDefaults.standard or SKPaymentQueue.default() or UIApplication.shared
    static var shared = FirebaseManager()

    func createEvent(name: String, timeStamp: [String:String], uid: String) {
        let postNameObject = [
            "EventName": name,
            "timestamp": timeStamp,
            "userID": uid
        ] as [String:Any]

        postName.setValue(postNameObject, withCompletionBlock: { error, ref in
            if error == nil {
                self.dismiss(animated: true, completion: nil)
            } else {
                //Do something
            }
        })
        let childautoID = postName.key

        //Whatever else you need to do in the function below here...

    }

}

用法:

class SomeViewController: UIViewController {

    @IBOutlet var nameTextField: UITextField!

    //Some code...

    @IBAction func createEventButtonPressed(_ sender: Any) {
        FirebaseManager.shared.createEvent(name: nameTextField.text, timeStamp: [".sv":"timestamp"], uid: Auth.auth().currentUser!.uid)
    }

    //Some more code...
}

同样，您可以在我们的 FirebaseManager 类中添加一个类型为 String 的名为 lastKey 的值。请注意我们添加到 FirebaseManager 类顶部的变量:

class FirebaseManager {

    var lastKey: String!

    static var shared = FirebaseManager()

    func createEvent(name: String, timeStamp: [String:String], uid: String) {
        let postNameObject = [
            "EventName": name,
            "timestamp": timeStamp,
            "userID": uid
        ] as [String:Any]

        postName.setValue(postNameObject, withCompletionBlock: { error, ref in
            if error == nil {
                self.dismiss(animated: true, completion: nil)
            } else {
                //Do something
            }
        })
        let childautoID = postName.key

        //Whatever else you need to do in the function below here...

    }

}

同样，我们可以在一个 View Controller 中设置这个值:

class ViewControllerA: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        FirebaseManager.shared.lastKey = "aBcDeFg9876543210"
    }
}

然后在前一个 View Controller 之后加载的另一个 View Controller 中获取此值:

class ViewControllerB: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        print(FirebaseManager.shared.lastKey)
    }
}

打印:aBcDeFg9876543210

这就是美static关键词。您可以在此处了解有关创建单例类的更多信息:https://cocoacasts.com/what-is-a-singleton-and-how-to-create-one-in-swift