UITextFiled限制输入字符的数量

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    if([string isEqualToString:@"\n"]){
//按回车关闭键盘
        [textField resignFirstResponder];
        return NO;
    }else if (string.length == 0){
//判断是不是删除键
        return YES;
    }else if(self.nicknameText.text.length >= 10){
//输入的字符个数大于10，则无法继续输入，返回NO表示禁止输入
        return NO;
    }else{
        return YES;
    }
}