您应该使用此扩展,它与
   
    NumberFormatter
   
   :
  
  struct Number {
    static let formatterWithDots: NumberFormatter = {
        let formatter = NumberFormatter()
        formatter.groupingSeparator = "." // only include this if you want to use dots regardless of the locale
        formatter.numberStyle = .decimal
        return formatter
    }()
}
extension Double {
    var formattedWithDots: String? {
        return Number.formatterWithDots.string(from: self as NSNumber)
    }
}
  
   
   
  
  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(textFieldDidChange), name: .UITextFieldTextDidChange, object: nil)
}
override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    NotificationCenter.default.removeObserver(self)
}
@objc fileprivate func textFieldDidChange() {
    if let number = Double(textField.text ?? "") {
        textField.text = number.formattedWithDots
    }
}