thinkphp验证用户名是否重复

<?php 
 /** 
 * Created by PhpStorm.  
 */ 
 namespace Admin\Model; 
 use Think\Model; 
 class UserModel extends Model { 
    //自动验证 
    protected $_validate=array( 
        //array(验证字段，验证规则，错误提示，验证条件，附加规则，验证时间) 或者单独留给注册用，登陆单独写规则 
        array('user_name','','帐号名称已经存在！',0,'unique',1), 
        array('user_name','require','用户名不能为空',self::EXISTS_VALIDATE), 
        array('user_name', '5,20', '用户名长度5-20位！', self::EXISTS_VALIDATE,'length'), 
        array('password','require','密码不能为空',self::EXISTS_VALIDATE), 
        array('code','require','验证码不能为空',self::EXISTS_VALIDATE), 
        array('password', '5,30', '密码长度不合法！', self::EXISTS_VALIDATE,'length'), 
        array('repassword', 'password', '俩次输入密码不一致！', self::EXISTS_VALIDATE,'confirm'), 
        array('code', '4', '请输入4位验证码', self::EXISTS_VALIDATE,'length'), 
    ); 
    //使用create方法创建数据对象的时候,执行Add()方法时，不在$insertFields定义范围内的字段将直接丢弃即只允许新增定义内的字段 
    protected $insertFields = array('id','user_name','password','user_byname','reg_time','reg_ip','login_time','login_count','role_id','status','unqi_id'); 
    //使用create方法更新数据对象的时候,执行sava()方法时，不在$updateFields定义范围内的字段将直接丢弃 
    protected $updateFields = array('id','user_name','password','user_byname','reg_time','reg_ip','login_time','login_count','role_id','status','unqi_id'); 
    //自动完成 
    protected $_auto=array( 
        array('password', 'sha1', self::MODEL_INSERT, 'function'), 
        array('login_time', 'time', self::MODEL_INSERT, 'function'), 
        array('reg_time','time',self::MODEL_INSERT,'function'), 
        array('reg_ip','get_client_ip',self::MODEL_INSERT,'function'), 
        array('login_ip','get_client_ip',self::MODEL_BOTH,'function'), 
        array('login_time','time',self::MODEL_BOTH,'function'), 
        array('login_count',0,self::MODEL_INSERT), 
        array('status',1,self::MODEL_INSERT), 
        array('password','',self::MODEL_UPDATE,'ignore'),//修改时空白则忽略 
    ); 
    //检帐帐户是否存在或者停用状态 
    public function checkStatus($username){ 
        $map=array(); 
        $map['user_name']=$username; 
        $map['status']=array('gt',0); 
        return $authInfo=$this->where($map)->find(); 
    } 
    //验证登陆 
    public function checkLogin($username,$password,$code){ 
        $data=array( 
            'user_name'=>$username, 
            'password'=>$password, 
            'code'=>$code, 
        ); 
        if(!$this->create($data)) return $this->getError(); 
        //检测用户名是否存在或状态 
        if($authInfo=$this->checkStatus($username)){ 
         return  $authInfo; 
        } 
    } 
    //登陆后更新数据库登陆时间和次数级ip 
    public function update($user_id,$login_count){ 
        $data = array( 
            'login_time'=>time(), 
            'login_ip'=>get_client_ip(), 
            'login_count'=>$login_count+1 
        ); 
       return $this-> where('id='.$user_id )->setField($data); 
    } 
    //注册管理员 
    public function register($username,$re_name,$byname,$password){ 
        $data=array( 
            're_name'=>$re_name, 
            'user_name'=>$username, 
            'user_byname'=>$byname, 
            'password'=>$password, 
        ); 
        if(!$this->create($data)){ 
            return $this->getError(); 
        }else{ 
            P($data); 
            echo  $this->add(); 
        } 
    } 
 }