AngularJS - Server side validation and client side forms

Question

I am trying to understand how to do the following things:

What is the accepted way of declaring a form. My understanding is you just declare the form in HTML, and add ng-model directives like so:

ng-model="item.name"

What to send to the server. I can just send the item object to the server as JSON, and interpret it. Then I can perform validation on object. If it fails, I throw a JSON error, and send back what exactly? Is there an accepted way of doing this? How do I push validation errors from the server to the client in a nice way?

I really need an example, but Angulars docs are pretty difficult to understand.

Edit: It seems I've phrased my question poorly.

I know how to validate client side, and how to handle error/success as promise callbacks. What I want to know, is the accepted way of bundling SERVER side error messages to the client. Say I have a username and password signup form. I don't want to poll the server for usernames and then use Angular to determine a duplicate exists. I want to send the username to the server, validate no other account exists with the same name, and then submit form. If an error occurs, how do I send it back?

What about pushing the data to the server as is (keys and values) with an error field appended like so:

{
  ...data...

  "errors": [
    {
      "context": null,
      "message": "A detailed error message.",
      "exceptionName": null
    }
  ]
}

Then binding to the DOM.

Answer 1

I've also been playing around with this kind of thing recently and I've knocked up this demo. I think it does what you need.

Setup your form as per normal with any particular client side validations you want to use:

<div ng-controller="MyCtrl">
    <form name="myForm" onsubmit="return false;">
        <div>
            <input type="text" placeholder="First name" name="firstName" ng-model="firstName" required="true" />
            <span ng-show="myForm.firstName.$dirty && myForm.firstName.$error.required">You must enter a value here</span>
            <span ng-show="myForm.firstName.$error.serverMessage">{{myForm.firstName.$error.serverMessage}}</span>
        </div>
        <div>
            <input type="text" placeholder="Last name" name="lastName" ng-model="lastName"/>
            <span ng-show="myForm.lastName.$error.serverMessage">{{myForm.lastName.$error.serverMessage}}</span>
        </div>
        <button ng-click="submit()">Submit</button>
    </form>
</div>

Note also I have added a serverMessage for each field:

<span ng-show="myForm.firstName.$error.serverMessage">{{myForm.firstName.$error.serverMessage}}</span>

This is a customisable message that comes back from the server and it works the same way as any other error message (as far as I can tell).

Here is the controller:

function MyCtrl($scope, $parse) {
      var pretendThisIsOnTheServerAndCalledViaAjax = function(){
          var fieldState = {firstName: 'VALID', lastName: 'VALID'};
          var allowedNames = ['Bob', 'Jill', 'Murray', 'Sally'];
          
          if (allowedNames.indexOf($scope.firstName) == -1) fieldState.firstName = 'Allowed values are: ' + allowedNames.join(',');
          if ($scope.lastName == $scope.firstName) fieldState.lastName = 'Your last name must be different from your first name';
          
          return fieldState;
      };
      $scope.submit = function(){
          var serverResponse = pretendThisIsOnTheServerAndCalledViaAjax();

          for (var fieldName in serverResponse) {
              var message = serverResponse[fieldName];
              var serverMessage = $parse('myForm.'+fieldName+'.$error.serverMessage');
              
              if (message == 'VALID') {
                  $scope.myForm.$setValidity(fieldName, true, $scope.myForm);
                  serverMessage.assign($scope, undefined);
              }
              else {
                  $scope.myForm.$setValidity(fieldName, false, $scope.myForm);
                  serverMessage.assign($scope, serverResponse[fieldName]);
              }
          }
      };
}

I am pretending to call the server in pretendThisIsOnTheServerAndCalledViaAjax you can replace it with an ajax call, the point is it just returns the validation state for each field. In this simple case I am using the value VALID to indicate that the field is valid, any other value is treated as an error message. You may want something more sophisticated!

Once you have the validation state from the server you just need to update the state in your form.

You can access the form from scope, in this case the form is called myForm so $scope.myForm gets you the form. (Source for the form controller is here if you want to read up on how it works).

You then want to tell the form whether the field is valid/invalid:

$scope.myForm.$setValidity(fieldName, true, $scope.myForm);

or

$scope.myForm.$setValidity(fieldName, false, $scope.myForm);

We also need to set the error message. First of all get the accessor for the field using $parse. Then assign the value from the server.

var serverMessage = $parse('myForm.'+fieldName+'.$error.serverMessage');
serverMessage.assign($scope, serverResponse[fieldName]);

Answer 2

I've got similar solution as Derek, described on codetunes blog. TL;DR:

• display an error in similar way as in Derek's solution:

  <span ng-show="myForm.fieldName.$error.server">{{errors.fieldName}}</span>
  

• add directive which would clean up an error when user change the input:

  <input type="text" name="fieldName" ng-model="model.fieldName" server-error />
  
  angular.module('app').directive 'serverError', ->
    {
      restrict: 'A'
      require: '?ngModel'
      link: (scope, element, attrs, ctrl) ->
        element.on 'change', ->
          scope.$apply ->
            ctrl.$setValidity('server', true)
    }
  

• Handle an error by passing the error message to the scope and telling that form has an error:

  errorCallback = (result) ->
    # server will return something like:
    # { errors: { name: ["Must be unique"] } }
    angular.forEach result.data.errors, (errors, field) ->
      # tell the form that field is invalid
      $scope.form[field].$setValidity('server', false)
      # keep the error messages from the server
      $scope.errors[field] = errors.join(', ') 
  

Hope it would be useful :)

Answer 3

Well, the Answer Derek Ekins gave is very nice to work on. But: If you disable the submit button with ng-disabled="myForm.$invalid" - the button will not automatically go back to enabled as the server-based error state doesn't seem to be changed. Not even if you edit ALL fields in a form again to comply with valid inputs (based on client side validation).

Answer 4

By default, the form is submitted normally. If you don't provide a name property for each field in the form then it won't submit the correct data. What you can do is capture the form before it submitted and submit that data yourself via ajax.

<form ng-submit="onSubmit(); return false">

And then in your $scope.onSubmit() function:

$scope.onSubmit = function() {
  var data = {
    'name' : $scope.item.name
  };
  $http.post(url, data)
    .success(function() {
    })
    .failure(function() {

    });
};

You can also validate the data by setting up required attributes.

Answer 5

If you choose ngResource, it would look like this

var Item = $resource('/items/');
$scope.item = new Item();
$scope.submit = function(){
  $scope.item.$save(
    function(data) {
        //Yahooooo :)
    }, function(response) {
        //oh noooo :(
        //I'm not sure, but your custom json Response should be stick in response.data, just inspect the response object 
    }
  );
};

The most important thing is, that your HTTP-Response code have to be a 4xx to enter the failure callback.

Answer 6

As of July 2014, AngularJS 1.3 has added new form validation features. This includes ngMessages and asyncValidators so you can now fire server side validation per field prior to submitting the form.

Angular 1.3 Form validation tutorial :

• Taming forms in Angular 1.3
• Video | Repo | Demo

References:

• ngMessages directive
• ngModel.NgModelController

Answer 7

I needed this in a few projects so I created a directive. Finally took a moment to put it up on GitHub for anyone who wants a drop-in solution.

https://github.com/webadvanced/ng-remote-validate

Features:

• Drop in solution for Ajax validation of any text or password input

• Works with Angulars build in validation and cab be accessed at formName.inputName.$error.ngRemoteValidate

• Throttles server requests (default 400ms) and can be set with ng-remote-throttle="550"

• Allows HTTP method definition (default POST) with ng-remote-method="GET" Example usage for a change password form that requires the user to enter their current password as well as the new password.:

  Change password

  Current Required Incorrect current password. Please enter your current account password.

  <label for="newPassword">New</label>
  <input type="password"
         name="newPassword"
         placeholder="New password"
         ng-model="password.new"
         required>
  
  <label for="confirmPassword">Confirm</label>
  <input ng-disabled=""
         type="password"
         name="confirmPassword"
         placeholder="Confirm password"
         ng-model="password.confirm"
         ng-match="password.new"
         required>
  <span ng-show="changePasswordForm.confirmPassword.$error.match">
      New and confirm do not match
  </span>
  
  <div>
      <button type="submit" 
              ng-disabled="changePasswordForm.$invalid" 
              ng-click="changePassword(password.new, changePasswordForm);reset();">
          Change password
      </button>
  </div>
  

Answer 8

As variant

// ES6 form controller class

class FormCtrl {
 constructor($scope, SomeApiService) {
   this.$scope = $scope;
   this.someApiService = SomeApiService;
   this.formData = {};
 }

 submit(form) {
   if (form.$valid) {
     this.someApiService
         .save(this.formData)
         .then(() => {
           // handle success

           // reset form
           form.$setPristine();
           form.$setUntouched();

           // clear data
           this.formData = {};
         })
         .catch((result) => {
           // handle error
           if (result.status === 400) {
             this.handleServerValidationErrors(form, result.data && result.data.errors)
           } else {// TODO: handle other errors}
         })
   }
 }

 handleServerValidationErrors(form, errors) {
  // form field to model map
  // add fields with input name different from name in model
  // example: <input type="text" name="bCategory" ng-model="user.categoryId"/>
  var map = {
    categoryId: 'bCategory',
    // other
  };

  if (errors && errors.length) {
    // handle form fields errors separately
    angular.forEach(errors, (error) => {
      let formFieldName = map[error.field] || error.field;
      let formField = form[formFieldName];
      let formFieldWatcher;

      if (formField) {
        // tell the form that field is invalid
        formField.$setValidity('server', false);

        // waits for any changes on the input
        // and when they happen it invalidates the server error.
        formFieldWatcher = this.$scope.$watch(() => formField.$viewValue, (newValue, oldValue) => {
          if (newValue === oldValue) {
            return;
          }

          // clean up the server error
          formField.$setValidity('server', true);

          // clean up form field watcher
          if (formFieldWatcher) {
            formFieldWatcher();
            formFieldWatcher = null;
          }
        });
      }
    });

  } else {
    // TODO: handle form validation
    alert('Invalid form data');
  }
}

Answer 9

As I understand the question is about passing errors from the server to the client. I'm not sure if there are well-established practices. So I'm going to describe a possible approach:

<form name="someForm" ng-submit="submit()" ng-controller="c1" novalidate>
    <input name="someField" type="text" ng-model="data.someField" required>
    <div ng-show="someForm.$submitted || someForm.someField.$touched">
        <div ng-show="someForm.someField.$error.required" class="error">required</div>
        <div ng-show="someForm.someField.$error.someError" class="error">some error</div>
    </div>
    <input type="submit">
</form>

Let's say a server returns an object of the following kind:

{errors: {
    someField: ['someError'],
}}

Then you can pass the errors to the UI this way:

Object.keys(resp.errors).forEach(i => {
    resp.errors[i].forEach(c => {
        $scope.someForm[i].$setValidity(c, false);
        $scope.someForm[i].$validators.someErrorResetter
            = () => $scope.someForm[i].$setValidity(c, true);
    });
});

I make each field invalid and add a validator (which is not really a validator). Since validators are called after every change, this let's us reset the error status.

You can experiment with it here. You might also want to check out ngMessages. And a couple of related articles.