ios - 如何检查 UITextField 何时发生变化？

Question

我正在尝试检查文本字段何时发生更改，也相当于用于 textView 的函数 - textViewDidChange 到目前为止我已经这样做了:

  func textFieldDidBeginEditing(textField: UITextField) {
        if self.status.text == "" && self.username.text == "" {
            self.topRightButton.enabled = false
        } else {   
            self.topRightButton.enabled = true
        }
    }

哪一种有效，但是一旦按下文本字段，topRightButton就会启用，我希望它仅在实际输入文本时才启用？

Answer 1

SWIFT

swift 4.2

textfield.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)), for: .editingChanged)

和

@objc func textFieldDidChange(_ textField: UITextField) {

}

SWIFT 3 和 swift 4.1

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)), for: .editingChanged)

和

func textFieldDidChange(_ textField: UITextField) {

}

SWIFT 2.2

textField.addTarget(self, action: #selector(ViewController.textFieldDidChange(_:)), forControlEvents: UIControlEvents.EditingChanged)

和

func textFieldDidChange(textField: UITextField) {
    //your code
}

objective-C

[textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];

而textFieldDidChange方法是

-(void)textFieldDidChange :(UITextField *) textField{
    //your code
}