swift3.0 对UITextField()输入框输入的内容进行监控

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首先需要继承 UITextFieldDelegate

class TestViewController: UIViewController,UITextFieldDelegate{}

添加事件委托

textField.delegate = self

点击输入框时触发以下事件：

func textFieldDidBeginEditing(_ textField: UITextField){}

我的需求为输入一百以内最多为两位小数，使用以下方式对输入的值进行实时监控

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool { var newString = (textField.text! as NSString).replacingCharacters(in: range, with: string)
let expression = "^[0-9]*(?:\\.[0-9]{0,2})?$" do {
let regex: NSRegularExpression = try NSRegularExpression(pattern: expression, options: NSRegularExpression.Options.caseInsensitive)
let numberOfMatches = regex.matches(in: newString, options: NSRegularExpression.MatchingOptions.reportProgress, range: NSMakeRange(0, newString.characters.count)) if numberOfMatches.count == 0{
return false
}else{ if newString != "" {
if newString[newString.startIndex] == "." {
newString = "0" + newString
} if newString[newString.index(before: newString.endIndex)] == "." {
newString = newString + "0"
} if (Double(newString)! > 100.0){
account_textfield.text = "100"
return false
}
}
return true
}
}
catch {
return false
}
}