如何在UITextFIeld中将图标/图像放在文本的最后一个字母旁边？

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {
    let textField = UITextField()
    let iconImageView = UIImageView(image: UIImage(named: "icon"))

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置UITextField的属性
        textField.borderStyle = .roundedRect
        textField.placeholder = "请输入文本"
        textField.delegate = self
        
        // 添加UITextField和UIImageView到自定义的UIView中
        let customView = UIView()
        customView.addSubview(textField)
        customView.addSubview(iconImageView)
        
        // 设置布局约束
        textField.translatesAutoresizingMaskIntoConstraints = false
        iconImageView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            textField.leadingAnchor.constraint(equalTo: customView.leadingAnchor),
            textField.topAnchor.constraint(equalTo: customView.topAnchor),
            textField.bottomAnchor.constraint(equalTo: customView.bottomAnchor),
            iconImageView.leadingAnchor.constraint(equalTo: textField.trailingAnchor, constant: 5),
            iconImageView.centerYAnchor.constraint(equalTo: textField.centerYAnchor),
            iconImageView.widthAnchor.constraint(equalToConstant: 20),
            iconImageView.heightAnchor.constraint(equalToConstant: 20)
        ])
        
        // 将自定义的UIView添加到父视图中
        view.addSubview(customView)
        
        // 设置布局约束
        customView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            customView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            customView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            customView.widthAnchor.constraint(equalToConstant: 250),
            customView.heightAnchor.constraint(equalToConstant: 40)
        ])
    }
    
    // UITextField的代理方法，监听文本变化事件
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        // 获取文本的最后一个字母的位置
        let lastCharacterIndex = textField.text?.index((textField.text?.endIndex)!, offsetBy: -1)
        
        // 计算图标/图像的位置
        let iconXPosition = textField.frame.size.width - 20
        
        // 设置UIImageView的frame
        iconImageView.frame = CGRect(x: iconXPosition, y: 0, width: 20, height: 20)
        
        return true
    }
}