directive angularjs to check mail used or not - angularjs

Question

i want to check if email is already used or not (communication with back-end) but the error message is not shown in the screen.
the verficiation function service :
demoApp.factory('verifyEmail', function($http) {
return function(mail) {
var test=mail;
var urll="http://localhost:8080/app/personne/verifmail?msg=";
var aplrest=urll+test;
var ch3=aplrest;
return $http.post(ch3)
};});
the directive (with the help of #jsonmurphy)
demoApp.directive('existTo', ["$q","verifyEmail",function ($q, verifyEmail) {
return {
require: "ngModel",
scope: {
otherModelValue: "=existTo"
},
link: function(scope, element, attributes, ngModel) {
// Note the change to $asyncValidators here <-------------
ngModel.$asyncValidators.existTo = function(modelValue) {
var deferred = $q.defer();
verifyEmail(modelValue).then(function(respons) {
// the respons can be {exist="true"} or{exist="false"}
var rep=respons.exist;
deferred.resolve(rep);
});
return deferred.promise;
};
scope.$watch("otherModelValue", function() {
ngModel.$validate();
});
}
}; }]);
the html file:
<label>Email</label>
<input type="email" name="email" class="form-group"
ng-model="registration.user.email"
ng-pattern="/^[_a-z0-9]+(\.[_a-z0-9]+)*#[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,8})$/"
required exist-To="registration.user.email"/>
<span style="color:red" ng-show="registrationForm.email.$dirty && registrationForm.email.$invalid">
<span ng-show="registrationForm.email.$error.required">champs email obligatoire.</span>
<span ng-show="registrationForm.email.$error.pattern">Invalid email address.</span>
<span ng-show="registrationForm.email.$error.existTo">mail already exist.</span>
</span>

Answer 1

this the solution
demoApp.directive('existTo', ["$q","verifyEmail",function ($q, verifyEmail) {
return {
require: "ngModel",
scope: {
otherModelValue: "=existTo"
},
link: function(scope, element, attributes, ngModel) {
// Note the change to $asyncValidators here <-------------
ngModel.$asyncValidators.existTo = function(modelValue) {
var deferred = $q.defer();
// window.alert("l email a tester "+modelValue);
verifyEmail(modelValue).success(function(respons) {
// the respons can be {exist="true"} or{exist="false"}
// window.alert("la reponse " +respons);
var rep=respons.exist;
// window.alert("la reponse " +rep);
if (rep =="false") {
// The username is available
deferred.resolve();
} else {
deferred.reject();
}
});
return deferred.promise;
};
scope.$watch("otherModelValue", function() {
ngModel.$validate();
});
}
}; }]);