在Swift中设置UITextField的最大字符长度 [英] Set the maximum character length of a UITextField in Swift

问题描述

我知道还有其他主题，但我似乎无法找到如何实现它。

I know there are other topics on this but I can't seem to find out how to implement it.

我正在尝试将UITextField限制为仅5个字符

I'm trying to limit a UITextField to only 5 Characters

最好使用字母数字和 - 和。和_

Preferably Alphanumeric and - and . and _

我见过这段代码

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 
}

我只是不知道如何实际实现它，或者我应该换出哪个textfield用于我的自定义命名UITextField

I just don't know how to actually implement it or which "textfield" should I swap out for my custom named UITextField

推荐答案

1. 您的视图控制器应符合 UITextFieldDelegate ，如下所示：

class MyViewController: UIViewController, UITextFieldDelegate {

}

设置文本字段的委托： myTextField.delegate = self

所有在一起：

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
}

只允许将指定的字符集输入给定的文本字段

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

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

  return result
}

如何编写仅包含最大长度的数字输入的iOS文本字段

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