ios - 在 Swift 中设置 UITextField 的最大字符长度

Question

我知道还有其他关于此的主题，但我似乎无法找到如何实现它。

我试图将 UITextField 限制为仅五个字符。

最好是字母数字、-、. 和 _。

我看过这段代码:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange,
                       replacementString string: String) -> Bool
{
    let maxLength = 4
    let currentString: NSString = textField.text
    let newString: NSString =
             currentString.stringByReplacingCharactersInRange(range, withString: string)
    return newString.length <= maxLength
}

和

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

    let length = count(textField.text.utf16) + count(string.utf16) - range.length
    return length <= 10
}

我如何实际实现它？我应该用自定义命名的 UITextField 换掉哪个“文本字段”？

Answer 1

1. 您的 View Controller 应符合 UITextFieldDelegate，如下所示:

   class MyViewController: UIViewController, UITextFieldDelegate {
   
   }
   

2. 设置文本框的代理:myTextField.delegate = self

3. 在您的 View Controller 中实现该方法:

   textField(_:shouldChangeCharactersInRange:replacementString:)
   

一起:

class MyViewController: UIViewController, UITextFieldDelegate  // Set delegate to class

@IBOutlet var mytextField: UITextField             //  textfield variable

override func viewDidLoad() {
    super.viewDidLoad()
    mytextField.delegate = self                  // set delegate
}


func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange,
                       replacementString string: String) -> Bool
{
    let maxLength = 4
    let currentString: NSString = textField.text
    let newString: NSString =  currentString.stringByReplacingCharactersInRange(range, withString: string)

    return newString.length <= maxLength
}

对于 Swift 4

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let maxLength = 1
    let currentString: NSString = (textField.text ?? "") as NSString
    let newString: NSString =  currentString.replacingCharacters(in: range, with: string) as NSString

    return newString.length <= maxLength
}

对于 Swift 5

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    let maxLength = 1
    let currentString = (textField.text ?? "") as NSString
    let newString = currentString.replacingCharacters(in: range, with: string)

    return newString.count <= maxLength
}

只允许在给定的文本字段中输入一组指定的字符

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    var result = true

    if mytextField == textField {
        if count(string) > 0 {
            let disallowedCharacterSet = NSCharacterSet(charactersInString: "0123456789.-").invertedSet
            let replacementStringIsLegal = string.rangeOfCharacterFromSet(disallowedCharacterSet) == nil
            result = replacementStringIsLegal
        }
    }

    return result
}

How to program an iOS text field that takes only numeric input with a maximum length