如何使用另一个类的选择器？

Question

我有一个名为 FooFramework 的 Cocoa Touch 框架。

在其中，我想在键盘显示时管理选定视图在 Y 轴上的向上移动。我创建了一个KeyboardManager 类。下面是它的外观：

import UIKit

public class KeyboardManager {
    var notifyFromObject: Any?
    var observer: Any
    public var viewsToPushUp: [UIView] = []

    public init(observer: Any, viewsToPushUp: [UIView], notifyFromObject: Any? = nil) {
        self.observer = observer
        self.notifyFromObject = notifyFromObject
        self.viewsToPushUp = viewsToPushUp
    }

    public func pushViewsUpWhenKeyboardWillShow(){
        let notificationCenter = NotificationCenter.default
        print(self)
        notificationCenter.addObserver(self.observer, selector: #selector(FooFramework.KeyboardManager.pushViewsUp), name: NSNotification.Name.UIKeyboardWillShow, object: notifyFromObject)
    }

    @objc public func pushViewsUp(notification: NSNotification) {
        if let keyboardRectValue = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            let keyboardHeight = keyboardRectValue.height

            for view in viewsToPushUp {
                view.frame.origin.y -= keyboardHeight
            }
        }
    }
}

然后，我将这个 FooFramework 导入到一个名为 Bar 的 iOS 应用程序中。为了测试 FooFramework，我想推一个UITextField。代码如下：

import UIKit
import FooFramework

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        let kb = KeyboardManager(observer: self, viewsToPushUp: [textField], notifyFromObject: nil)
        kb.pushViewsUpWhenKeyboardWillShow()
    }

    func pushViewsUp(notification: NSNotification) {
        print("This should not be printed")
    }
}

我的问题是This should not be printed 出现在控制台中，而KeyboardManager 中的pushViewsUp 方法永远不会被调用。尽管我为选择器使用了完全限定的名称，但它坚持使用 ViewController 中的 pushViewsUp。这让我发疯了。

如果我从 ViewController 中删除 pushViewsUp，我会收到以下错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Bar.ViewController pushViewsUpWithNotification:]: unrecognized selector sent to instance 0x7fc540702d80'

我需要做什么才能使选择器正确指向FooFramework.KeyboardManager.pushViewsUp？

Answer 1

我相信您需要在addObserver 函数中使用self 而不是self.observer 作为观察者。

您还需要在函数范围之外声明kb 变量，以便管理器检测到通知。

例子：

import UIKit
import FooFramework

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!

    var kb: KeyboardManager?

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        kb = KeyboardManager(observer: self, viewsToPushUp: [textField], notifyFromObject: nil)
        kb?.pushViewsUpWhenKeyboardWillShow()
    }
}

KeyboardManager 变化：

public func pushViewsUpWhenKeyboardWillShow() {
    let notificationCenter = NotificationCenter.default
    print(self)
    notificationCenter.addObserver(self, 
                                   selector: #selector(FooFramework.KeyboardManager.pushViewsUp), 
                                   name: NSNotification.Name.UIKeyboardWillShow, 
                                   object: notifyFromObject)
}

Answer 2

除了贾斯汀建议的完全正确的建议之外，在您完全解决问题之前，还需要考虑一些其他事项。

1. KeyBoardManager 类实例本身将观察keyboardWillMoveUp 通知，因此您的

var 观察者：任意

里面是没有必要的。你应该删除它。

1. 我还将 addObserver 部分放在 KeyBoardManager 类本身的 init 中，这样就可以避免这个额外的调用 pushViewsUpWhenKeyboardWillShow() ，这似乎什么也没做。由于 KeyBoardManager 类应该只做这个，我不明白为什么添加观察者应该是另一个函数调用。

这就是您的 KeyboardManager 类的外观：

import UIKit

public class KeyboardManager {

    var notifyFromObject: Any?
    public var viewsToPushUp: [UIView] = []

    public init(viewsToPushUp: [UIView], notifyFromObject: Any? = nil){
        self.notifyFromObject = notifyFromObject
        self.viewsToPushUp = viewsToPushUp

//remember KeyboardManager itself is observing the notifications and moving the views it received from the ViewController. Hence we use self.
        NotificationCenter.default.addObserver(self, selector: #selector(FooFramework.KeyboardManager.pushViewsUp), name: NSNotification.Name.UIKeyboardWillShow, object: notifyFromObject)
    }

    @objc public func pushViewsUp(notification: NSNotification) {
        if let keyboardRectValue = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
            let keyboardHeight = keyboardRectValue.height

            for view in viewsToPushUp {
                view.frame.origin.y -= keyboardHeight
            }
        }
    }
}

1. 您还需要正确处理框架，然后才能从中获得正确的行为。

2. 您应该延长 KeyboardManagerInstance 的生命周期，使其与具有 textField 的 ViewController 的生命周期一样长。您可以按照 Justin 的建议将其声明为 ViewController 中的实例变量。按照您的操作方式，您的 KeyboardManager 实例是一个局部变量，一旦函数超出范围，就会创建并立即释放该变量。要验证这一点，您可以将其添加到 KeyboardManager 类并检查：

     deinit {
       print("KeyboardManager is perhaps dying an untimely death.")
     }
   

最后你的 ViewController 类应该这样做

  import UIKit
  import FooFramework

  class ViewController: UIViewController {

@IBOutlet weak var textField: UITextField!

var kb: KeyboardManager?

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    kb = KeyboardManager(viewsToPushUp: [textField], notifyFromObject: nil)
   //observe that there is no observer param in the initializer and also no "pushViewsUpWhenKeyboardWillShow" call as that behavior has already been moved to init itself.
}

}