AngularJS - Forms

Forms

Controls (input, select, textarea) are ways for a user to enter data. A Form is a collection of controls for the purpose of grouping related controls together.

Form and controls provide validation services, so that the user can be notified of invalid input before submitting a form. This provides a better user experience than server-side validation alone because the user gets instant feedback on how to correct the error. Keep in mind that while client-side validation plays an important role in providing good user experience, it can easily be circumvented and thus can not be trusted. Server-side validation is still necessary for a secure application.

Simple form

The key directive in understanding two-way data-binding is ngModel. The ngModel directive provides the two-way data-binding by synchronizing the model to the view, as well as view to the model. In addition it provides an API for other directives to augment its behavior.

------------

index.html

----------------------

<div ng-controller="ExampleController">
  <form novalidate class="simple-form">
    Name: <input type="text" ng-model="user.name" /><br />
    E-mail: <input type="email" ng-model="user.email" /><br />
    Gender: <input type="radio" ng-model="user.gender" value="male" />male
    <input type="radio" ng-model="user.gender" value="female" />female<br />
    <input type="button" ng-click="reset()" value="Reset" />
    <input type="submit" ng-click="update(user)" value="Save" />
  </form>
  <pre>form = {{user | json}}</pre>
  <pre>master = {{master | json}}</pre>
</div>

<script>
  angular.module('formExample', [])
    .controller('ExampleController', ['$scope', function($scope) {
      $scope.master = {};

      $scope.update = function(user) {
        $scope.master = angular.copy(user);
      };

      $scope.reset = function() {
        $scope.user = angular.copy($scope.master);
      };

      $scope.reset();
    }]);
</script>

Binding to form and control state

A form is an instance of FormController. The form instance can optionally be published into the scope using the name attribute.

Similarly, an input control that has the ngModel directive holds an instance of NgModelController. Such a control instance can be published as a property of the form instance using the name attribute on the input control. The name attribute specifies the name of the property on the form instance.

This implies that the internal state of both the form and the control is available for binding in the view using the standard binding primitives.

This allows us to extend the above example with these features:

• Custom error message displayed after the user interacted with a control (i.e. when $touched is set)
• Custom error message displayed upon submitting the form ($submitted is set), even if the user didn't interact with a control

----------------

index.html

----------------

<div ng-controller="ExampleController">
  <form name="form" class="css-form" novalidate>
    Name:
    <input type="text" ng-model="user.name" name="uName" required="" />
    <br />
    <div ng-show="form.$submitted || form.uName.$touched">
      <div ng-show="form.uName.$error.required">Tell us your name.</div>
    </div>

    E-mail:
    <input type="email" ng-model="user.email" name="uEmail" required="" />
    <br />
    <div ng-show="form.$submitted || form.uEmail.$touched">
      <span ng-show="form.uEmail.$error.required">Tell us your email.</span>
      <span ng-show="form.uEmail.$error.email">This is not a valid email.</span>
    </div>

    Gender:
    <input type="radio" ng-model="user.gender" value="male" />male
    <input type="radio" ng-model="user.gender" value="female" />female
    <br />
    <input type="checkbox" ng-model="user.agree" name="userAgree" required="" />

    I agree:
    <input ng-show="user.agree" type="text" ng-model="user.agreeSign" required="" />
    <br />
    <div ng-show="form.$submitted || form.userAgree.$touched">
      <div ng-show="!user.agree || !user.agreeSign">Please agree and sign.</div>
    </div>

    <input type="button" ng-click="reset(form)" value="Reset" />
    <input type="submit" ng-click="update(user)" value="Save" />
  </form>
</div>

-------------------

script.js

-----------------

angular.module('formExample', [])
.controller('ExampleController', ['$scope', function($scope) {
  $scope.master = {};

  $scope.update = function(user) {
    $scope.master = angular.copy(user);
  };

  $scope.reset = function(form) {
    if (form) {
      form.$setPristine();
      form.$setUntouched();
    }
    $scope.user = angular.copy($scope.master);
  };

  $scope.reset();
}]);

Custom model update triggers

By default, any change to the content will trigger a model update and form validation. You can override this behavior using the ngModelOptions directive to bind only to specified list of events. I.e. ng-model-options="{ updateOn: 'blur' }" will update and validate only after the control loses focus. You can set several events using a space delimited list. I.e. ng-model-options="{ updateOn: 'mousedown blur' }"

 

If you want to keep the default behavior and just add new events that may trigger the model update and validation, add "default" as one of the specified events.

I.e. ng-model-options="{ updateOn: 'default blur' }"

The following example shows how to override immediate updates. Changes on the inputs within the form will update the model only when the control loses focus (blur event).

--------------

index.html

------------------

<div ng-controller="ExampleController">
  <form>
    Name:
    <input type="text" ng-model="user.name" ng-model-options="{ updateOn: 'blur' }" /><br />
    Other data:
    <input type="text" ng-model="user.data" /><br />
  </form>
  <pre>username = "{{user.name}}"</pre>
  <pre>userdata = "{{user.data}}"</pre>
</div>

 

 

 

------------------

script.js

---------------------

 

angular.module('customTriggerExample', [])
.controller('ExampleController', ['$scope', function($scope) {
  $scope.user = {};
}]);

 

Non-immediate (debounced) model updates

You can delay the model update/validation by using the debounce key with the ngModelOptions directive. This delay will also apply to parsers, validators and model flags like $dirty or $pristine.

I.e. ng-model-options="{ debounce: 500 }" will wait for half a second since the last content change before triggering the model update and form validation.

If custom triggers are used, custom debouncing timeouts can be set for each event using an object in debounce. This can be useful to force immediate updates on some specific circumstances (like blur events).

I.e. ng-model-options="{ updateOn: 'default blur', debounce: { default: 500, blur: 0 } }"

If those attributes are added to an element, they will be applied to all the child elements and controls that inherit from it unless they are overridden.

This example shows how to debounce model changes. Model will be updated only 250 milliseconds after last change.

-------------

index.html

---------------

<div ng-controller="ExampleController">
  <form>
    Name:
    <input type="text" ng-model="user.name" ng-model-options="{ debounce: 250 }" /><br />
  </form>
  <pre>username = "{{user.name}}"</pre>
</div>

 

 

------------------------

script.js

----------------------------

angular.module('debounceExample', [])
.controller('ExampleController', ['$scope', function($scope) {
  $scope.user = {};
}]);

 

 Custom Validation

Angular provides basic implementation for most common HTML5 input types: (text, number, url, email, date, radio, checkbox), as well as some directives for validation (required, pattern, minlength, maxlength, min, max).

With a custom directive, you can add your own validation functions to the $validators object on the ngModelController. To get a hold of the controller, you require it in the directive as shown in the example below.

Each function in the $validators object receives the modelValue and the viewValue as parameters. Angular will then call $setValidity internally with the function's return value (true: valid, false: invalid). The validation functions are executed every time an input is changed ($setViewValue is called) or whenever the bound model changes. Validation happens after successfully running $parsers and $formatters, respectively. Failed validators are stored by key in ngModelController.$error.

Additionally, there is the $asyncValidators object which handles asynchronous validation, such as making an $http request to the backend. Functions added to the object must return a promise that must be resolved when valid or rejected when invalid. In-progress async validations are stored by key in ngModelController.$pending.

In the following example we create two directives:

• An integer directive that validates whether the input is a valid integer. For example, 1.23 is an invalid value, since it contains a fraction. Note that we validate the viewValue (the string value of the control), and not the modelValue. This is because input[number] converts the viewValue to a number when running the $parsers.
  
• A username directive that asynchronously checks if a user-entered value is already taken. We mock the server request with a $q deferred.
  

 

--------------

index.html

----------------------

<form name="form" class="css-form" novalidate>
  <div>
    Size (integer 0 - 10):
    <input type="number" ng-model="size" name="size"
           min="0" max="10" integer />{{size}}<br />
    <span ng-show="form.size.$error.integer">The value is not a valid integer!</span>
    <span ng-show="form.size.$error.min || form.size.$error.max">
      The value must be in range 0 to 10!</span>
  </div>

  <div>
    Username:
    <input type="text" ng-model="name" name="name" username />{{name}}<br />
    <span ng-show="form.name.$pending.username">Checking if this name is available...</span>
    <span ng-show="form.name.$error.username">This username is already taken!</span>
  </div>

</form>

 

---------------------

script.js

----------------------------

var app = angular.module('form-example1', []);

var INTEGER_REGEXP = /^\-?\d+$/;
app.directive('integer', function() {
  return {
    require: 'ngModel',
    link: function(scope, elm, attrs, ctrl) {
      ctrl.$validators.integer = function(modelValue, viewValue) {
        if (ctrl.$isEmpty(modelValue)) {
          // consider empty models to be valid
          return true;
        }

        if (INTEGER_REGEXP.test(viewValue)) {
          // it is valid
          return true;
        }

        // it is invalid
        return false;
      };
    }
  };
});

app.directive('username', function($q, $timeout) {
  return {
    require: 'ngModel',
    link: function(scope, elm, attrs, ctrl) {
    var usernames = ['Jim', 'John', 'Jill', 'Jackie'];

      ctrl.$asyncValidators.username = function(modelValue, viewValue) {

        if (ctrl.$isEmpty(modelValue)) {
          // consider empty model valid
          return $q.when();
        }

        var def = $q.defer();

        $timeout(function() {
          // Mock a delayed response
          if (usernames.indexOf(modelValue) === -1) {
            // The username is available
            def.resolve();
          } else {
            def.reject();
          }

        }, 2000);

        return def.promise;
      };
    }
  };
});