UITextView中的每个数字只允许一个小数(Swift 4)

import UIKit

class ViewController: UIViewController, UITextViewDelegate {
    
    @IBOutlet weak var textView: UITextView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        textView.delegate = self
    }
    
    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        // 获取当前文本内容
        let currentText = textView.text as NSString
        
        // 判断是否是数字输入
        let newText = currentText.replacingCharacters(in: range, with: text)
        let isNumeric = newText.isEmpty || (Double(newText) != nil)
        
        // 判断是否已经存在一个小数点
        let existingTextHasDecimalSeparator = currentText.range(of: ".")
        let replacementTextHasDecimalSeparator = text.range(of: ".")
        let isDecimalSeparatorEntered = existingTextHasDecimalSeparator != nil && replacementTextHasDecimalSeparator != nil
        
        // 返回是否允许输入
        return isNumeric && !isDecimalSeparatorEntered
    }
}