angularjs - Retrieved data in AngularsJS and Directive for checking if a username exists -

i follow solution checking if username present in db: defined in topic "angularjs: custom directive check if username exists"

in case, put in practice when user wants update data; script has launched when user wants change lastname.

at beginning, script should not display error message

here my controller:

// directive checking if username used app.directive('usernameavailable', function($timeout, $q, $http, contactservice) {   return {     restrict: 'ae',     require: 'ngmodel',     link: function(scope, elm, attr, model) {          model.interation=0;         model.$asyncvalidators.usernameexists = function() {            name= elm.val();         return contactservice.searchcontactbyname(name).success(function(contact){           $timeout(function(){             if(contact.length >0){                 model.$setvalidity('usernameexists', contact);                  //model.$setvalidity('unique', false); // validation criteria in form                 scope.alreadyexist='true';                 scope.contacts = contact;                        }else{                 model.$setvalidity('usernameexists', contact);                  //model.$setvalidity('unique', true); // validation criteria in form                 scope.alreadyexist='false';                              scope.contacts = null;                       }            }, 600);         });         };     }   }  });   app.controller('ctrleditcontacts', function ($scope, $routeparams, contactservice){      // load data user     contactservice.loadpersonbyid($routeparams.contactid).success(function(contact){         $scope.contact.id = contact[0].id;           $scope.contact.lastname = contact[0].lastname;           $scope.contact.firstname = contact[0].firstname;                 });  }); 

here my template:

  <div class="panel-body">     <form name="contactform" class="form-horizontal" role="form" novalidate ng-submit="submitform(contact)">        <div class="form-group">         <label for="username" class="col-sm-2 control-label">last name *</label>         <div class="col-sm-10">             <input type="text" class="form-control"             name="username" maxlength="100" placeholder="enter last name"             required             ng-model="contact.lastname"             username-available             ng-model-options="{ updateon: 'blur' }">             <div ng-if="contactform.$pending.usernameexists">checking....</div>              <div ng-show="alreadyexist=='true'" class="alert alert-info" role="alert" style="margin-top:10px;">               <span class="glyphicon glyphicon-alert" aria-hidden="true"></span>               <span class="sr-only">error:</span>               last name exists              </div>          </div>       </div>        <div class="form-group">         <label for="txtfirstname" class="col-sm-2 control-label">first name</label>         <div class="col-sm-10">           <input type="text" class="form-control" name="txtfirstname" maxlength="100" placeholder="enter first name" ng-model="contact.firstname">         </div>       </div> 

currently, script working. when page loaded data user correctly retrieved , displayed. script equally loaded , message "last name exists" appears. avoid , displays message when value of last name updated (and used).

could tell me how update script (of directive suppose) doing that?

thanks in advance help.