Swift 4 shouldChangeCharactersIn 只显示长度 = 12

Question

我有 textfield ,shouldChangeCharactersIn 代码，我使用条形码、系统和我的条形码代码 == 12 个字符。如果 barcode small 12 characters or big must be return false or clean text field ，我只想在我的字符串中显示 12 个字符。我的代码在下面。当我使用条形码时，如果我的条形码 12 个字符工作正常，但如果我读取 12 个字符低，请不要清除文本字段，

How can I fix it ?

下面是我的代码。

 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

        let length = (Mytext.text?.characters.count)! - range.length + string.characters.count
        if length == 13 {

            print("Mytext=\(Mytext.text!)")
            Mytext.text = ""

            return true

        }else {


            return true
        }


    }

读取12个字符条码时输出显示成功！当读取低 12 个字符时不要清除 Mytext 字段，当我再次读取时添加 +

Answer 1

您必须将替换字符串设置为“”空白字符串

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let length = (Mytext.text?.characters.count)! - range.length + string.characters.count
    if length == 13 {

        print("Mytext=\(Mytext.text!)")
        Mytext.text = ""

        return true

    }else {


        return true
    }


}

Answer 2

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    if (string != "" && textField.text?.count == 12) {

        print("Mytext = \(textField.text!)")
        textField.text = ""
        return false
    }

    return true
}

Swift 4 shouldChangeCharactersIn 只显示长度 = 12

Swift 4 shouldChangeCharactersIn only show length = 12

uitextfield

ios

swift