iOS短信验证码控件，自动输入回调两次解决办法

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldDidChangeValue:) name:UITextFieldTextDidChangeNotification object:_textField];

-(void)textFieldDidChangeValue:(UITextField *)textField{
}

[_textField addTarget:self action:@selector(valueChanged:) forControlEvents:UIControlEventEditingChanged];

-(void)valueChanged:(UITextField *)textField{
    UITextRange *selectedRange = textField.markedTextRange;//获取高亮部分
    if (selectedRange == nil || selectedRange.empty) {
    }else{
        return;
    }
}