AngularJS: integrating with server-side validation

This is another case where a custom directive is your friend. You'll want to create a directive and inject $http or $resource into it to make a call back to the server while you're validating.

Some pseudo code for the custom directive:

app.directive('uniqueEmail', function($http) {
  var toId;
  return {
    restrict: 'A',
    require: 'ngModel',
    link: function(scope, elem, attr, ctrl) { 
      //when the scope changes, check the email.
      scope.$watch(attr.ngModel, function(value) {
        // if there was a previous attempt, stop it.
        if(toId) clearTimeout(toId);

        // start a new attempt with a delay to keep it from
        // getting too "chatty".
        toId = setTimeout(function(){
          // call to some API that returns { isValid: true } or { isValid: false }
          $http.get('/Is/My/EmailValid?email=' + value).success(function(data) {

              //set the validity of the field
              ctrl.$setValidity('uniqueEmail', data.isValid);
          });
        }, 200);
      })
    }
  }
});

And here's how you'd use it in the mark up:

<input type="email" ng-model="userEmail" name="userEmail" required unique-email/>
<span ng-show="myFormName.userEmail.$error.uniqueEmail">Email is not unique.</span>

EDIT: a small explanation of what's happening above.

1. When you update the value in the input, it updates the $scope.userEmail
2. The directive has a $watch on $scope.userEmail it set up in it's linking function.
   • When the $watch is triggered it makes a call to the server via $http ajax call, passing the email
   • The server would check the email address and return a simple response like '{ isValid: true }
   • that response is used to $setValidity of the control.
3. There is a in the markup with ng-show set to only show when the uniqueEmail validity state is false.

... to the user that means:

1. Type the email.
2. slight pause.
3. "Email is not unique" message displays "real time" if the email isn't unique.

EDIT2: This is also allow you to use form.$invalid to disable your submit button.

I have created plunker with solution that works perfect for me. It uses custom directive but on entire form and not on single field.

http://plnkr.co/edit/HnF90JOYaz47r8zaH5JY

I wouldn't recommend disabling submit button for server validation.

Ok. In case if someone needs working version, it is here:

From doc:

 $apply() is used to enter Angular execution context from JavaScript

 (Keep in mind that in most places (controllers, services) 
 $apply has already been called for you by the directive which is handling the event.)

This made me think that we do not need: $scope.$apply(function(s) { otherwise it will complain about $digest

app.directive('uniqueName', function($http) {
    var toId;
    return {
        require: 'ngModel',
        link: function(scope, elem, attr, ctrl) {
            //when the scope changes, check the name.
            scope.$watch(attr.ngModel, function(value) {
                // if there was a previous attempt, stop it.
                if(toId) clearTimeout(toId);

                // start a new attempt with a delay to keep it from
                // getting too "chatty".
                toId = setTimeout(function(){
                    // call to some API that returns { isValid: true } or { isValid: false }
                    $http.get('/rest/isUerExist/' + value).success(function(data) {

                        //set the validity of the field
                        if (data == "true") {
                            ctrl.$setValidity('uniqueName', false);
                        } else if (data == "false") {
                            ctrl.$setValidity('uniqueName', true);
                        }
                    }).error(function(data, status, headers, config) {
                        console.log("something wrong")
                    });
                }, 200);
            })
        }
    }
});

HTML:

<div ng-controller="UniqueFormController">

        <form name="uniqueNameForm" novalidate ng-submit="submitForm()">

            <label name="name"></label>
            <input type="text" ng-model="name" name="name" unique-name>   <!-- 'unique-name' because of the name-convention -->

            <span ng-show="uniqueNameForm.name.$error.uniqueName">Name is not unique.</span>

            <input type="submit">
        </form>
    </div>

Controller might look like this:

app.controller("UniqueFormController", function($scope) {
    $scope.name = "Bob"
})

Thanks to the answers from this page learned about https://github.com/webadvanced/ng-remote-validate

Option directives, which is slightly less than I do not really liked, as each field to write the directive. Module is the same - a universal solution.

But in the modules I was missing something - check the field for several rules.
Then I just modified the module https://github.com/borodatych/ngRemoteValidate
Apologies for the Russian README, eventually will alter.
I hasten to share suddenly have someone with the same problem.
Yes, and we have gathered here for this...

Load:

<script type="text/javascript" src="../your/path/remoteValidate.js"></script>

Include:

var app = angular.module( 'myApp', [ 'remoteValidate' ] );

HTML

<input type="text" name="login" 
ng-model="user.login" 
remote-validate="( '/ajax/validation/login', ['not_empty',['min_length',2],['max_length',32],'domain','unique'] )" 
required
/>
<br/>
<div class="form-input-valid" ng-show="form.login.$pristine || (form.login.$dirty && rv.login.$valid)">
    From 2 to 16 characters (numbers, letters and hyphens)
</div>
<span class="form-input-valid error" ng-show="form.login.$error.remoteValidate">
    <span ng:bind="form.login.$message"></span>
</span>

BackEnd [Kohana]

public function action_validation(){

    $field = $this->request->param('field');
    $value = Arr::get($_POST,'value');
    $rules = Arr::get($_POST,'rules',[]);

    $aValid[$field] = $value;
    $validation = Validation::factory($aValid);
    foreach( $rules AS $rule ){
        if( in_array($rule,['unique']) ){
            /// Clients - Users Models
            $validation = $validation->rule($field,$rule,[':field',':value','Clients']);
        }
        elseif( is_array($rule) ){ /// min_length, max_length
            $validation = $validation->rule($field,$rule[0],[':value',$rule[1]]);
        }
        else{
            $validation = $validation->rule($field,$rule);
        }
    }

    $c = false;
    try{
        $c = $validation->check();
    }
    catch( Exception $e ){
        $err = $e->getMessage();
        Response::jEcho($err);
    }

    if( $c ){
        $response = [
            'isValid' => TRUE,
            'message' => 'GOOD'
        ];
    }
    else{
        $e = $validation->errors('validation');
        $response = [
            'isValid' => FALSE,
            'message' => $e[$field]
        ];
    }
    Response::jEcho($response);
}