在文本字段下方显示错误消息，如 android

如何解决在文本字段下方显示错误消息，如 android

我尝试使用此链接：https://stackoverflow.com/a/56742493/13547105

但是每次当我按下后退按钮或保存按钮时，我的应用程序就会崩溃

我的错误是：原因：'无法删除变量：978：0x280750b90.marker{id：2509} colIndex：262 from engine

import UIKit

private var rightViews = NSMapTable<UITextField,UIView>(keyOptions: NSPointerFunctions.Options.weakMemory,valueOptions: NSPointerFunctions.Options.strongMemory)
private var errorViews = NSMapTable<UITextField,valueOptions: NSPointerFunctions.Options.strongMemory)

extension UITextField {
    // Add/remove error message
    func setError(_ string: String? = nil,show: Bool = true) {
        if let rightView = rightView,rightView.tag != 999 {
            rightViews.setobject(rightView,forKey: self)
        }

        // Remove message
        guard string != nil else {
            if let rightView = rightViews.object(forKey: self) {
                self.rightView = rightView
                rightViews.removeObject(forKey: self)
            } else {
                self.rightView = nil
            }

            if let errorView = errorViews.object(forKey: self) {
                errorView.isHidden = true
                errorViews.removeObject(forKey: self)
            }

            return
        }

        // Create container
        let container = UIView()
        container.translatesAutoresizingMaskIntoConstraints = false

        // Create triangle
        let triagle = Triangletop()
        triagle.backgroundColor = .clear
        triagle.translatesAutoresizingMaskIntoConstraints = false
        container.addSubview(triagle)

        // Create red line
        let line = UIView()
        line.backgroundColor = .red
        line.translatesAutoresizingMaskIntoConstraints = false
        container.addSubview(line)

        // Create message
        let label = UILabel()
        label.text = string
        label.textColor = .white
        label.numberOfLines = 0
        label.font = UIFont.systemFont(ofSize: 15)
        label.backgroundColor = .black
        label.setContentCompressionResistancePriority(UILayoutPriority(rawValue: 250),for: .horizontal)
        label.translatesAutoresizingMaskIntoConstraints = false
        container.addSubview(label)

        // Set constraints for triangle
        triagle.heightAnchor.constraint(equalToConstant: 10).isActive = true
        triagle.widthAnchor.constraint(equalToConstant: 15).isActive = true
        triagle.topAnchor.constraint(equalTo: container.topAnchor,constant: -10).isActive = true
        triagle.trailingAnchor.constraint(equalTo: container.trailingAnchor,constant: -15).isActive = true

        // Set constraints for line
        line.heightAnchor.constraint(equalToConstant: 3).isActive = true
        line.topAnchor.constraint(equalTo: triagle.bottomAnchor,constant: 0).isActive = true
        line.leadingAnchor.constraint(equalTo: container.leadingAnchor,constant: 0).isActive = true
        line.trailingAnchor.constraint(equalTo: container.trailingAnchor,constant: 0).isActive = true

        // Set constraints for label
        label.topAnchor.constraint(equalTo: line.bottomAnchor,constant: 0).isActive = true
        label.bottomAnchor.constraint(equalTo: container.bottomAnchor,constant: 0).isActive = true
        label.leadingAnchor.constraint(equalTo: container.leadingAnchor,constant: 0).isActive = true
        label.trailingAnchor.constraint(equalTo: container.trailingAnchor,constant: 0).isActive = true

        if !show {
            container.isHidden = true
        }
        // superview!.superview!.addSubview(container)
        UIApplication.shared.keyWindow!.addSubview(container)

        // Set constraints for container
        container.widthAnchor.constraint(lessthanorEqualTo: superview!.widthAnchor,multiplier: 1).isActive = true
        container.trailingAnchor.constraint(equalTo: superview!.trailingAnchor,constant: 0).isActive = true
        container.topAnchor.constraint(equalTo: superview!.bottomAnchor,constant: 0).isActive = true

        // Hide other error messages
        let enumerator = errorViews.objectEnumerator()
        while let view = enumerator!.nextObject() as! UIView? {
            view.isHidden = true
        }

        // Add right button to textField
        let errorButton = UIButton(type: .custom)
        errorButton.tag = 999
        errorButton.setimage(UIImage(named: "ic_error"),for: .normal)
        errorButton.frame = CGRect(x: 0,y: 0,width: frame.size.height,height: frame.size.height)
        errorButton.addTarget(self,action: #selector(errorAction),for: .touchUpInside)
        rightView = errorButton
        rightviewmode = .always

        // Save view with error message
        errorViews.setobject(container,forKey: self)
    }

    // Show error message
    @IBAction
    func errorAction(_ sender: Any) {
        let errorButton = sender as! UIButton
        let textField = errorButton.superview as! UITextField

        let errorView = errorViews.object(forKey: textField)
        if let errorView = errorView {
            errorView.isHidden.toggle()
        }

        let enumerator = errorViews.objectEnumerator()
        while let view = enumerator!.nextObject() as! UIView? {
            if view != errorView {
                view.isHidden = true
            }
        }

        // Don't hide keyboard after click by icon
//        UIViewController.isCatchTappedAround = false
    }
}

class Triangletop: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func draw(_ rect: CGRect) {
        guard let context = UIGraphicsGetCurrentContext() else {
            return
        }

        context.beginPath()
        context.move(to: CGPoint(x: (rect.maxX / 2.0),y: rect.minY))
        context.addLine(to: CGPoint(x: rect.maxX,y: rect.maxY))
        context.addLine(to: CGPoint(x: (rect.minX / 2.0),y: rect.maxY))
        context.closePath()

        context.setFillColor(UIColor.red.cgColor)
        context.fillPath()
    }
}

Viewcontroller.swift

import UIKit

class FormEditProfileInfoController: UIViewController,UITextFieldDelegate {

@IBOutlet weak var txtPOBox: UITextField!

override func viewDidLoad() {
     txtPOBox.delegate = self
}

@IBAction func actionBack(_ sender: Any) {
        dispatchQueue.main.async {
            self.dismiss(animated: true,completion: nil)
    }
}

@IBAction func actionSave(_ sender: Any) {
     let poBox = txtPOBox.text ?? ""
     if poBox.count <= 0 {
             txtPOBox.setError("er_enter_po_Box".localizedstr(),show: true)
             return false
     }
    txtPOBox.setError()
    return true
}

func textField(_ textField: UITextField,shouldChangeCharactersIn range: NSRange,replacementString string: String) -> Bool {
            textField.setError()
            return true
        }

}

感谢您的帮助