你的视图控制器应该符合以下代码中所示的UITextFieldDelegate
:
class MyViewController: UIViewController, UITextFieldDelegate {
}
设置文本框的代理:myTextField.delegate = self
在您的视图控制器中实现该方法:
textField(_:shouldChangeCharactersInRange:replacementString:)
全部在一起:
class MyViewController: UIViewController, UITextFieldDelegate // Set delegate to class
@IBOutlet var mytextField: UITextField // textfield variable
override func viewDidLoad() {
super.viewDidLoad()
mytextField.delegate = self
}
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版本
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
}
适用于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
}
仅允许在指定的文本字段中输入特定字符
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
}
如何编程iOS文本框,仅接受数字输入并具有最大长度限制
String
的长度,现在你终于可以用.prefix(n)来实现了。 - Fattie