Basic Usage with Built-In Validators
To begin, first we need to make sure that we have a reference to angular.js file. Then we need to do the following steps:
- give a name to our form
- put novalidate="" attribute on the form
So we should have something like this on our form:
<form name="myForm" novalidate="" ng-submit="" > . . . </form>- add a unique name to each input field
- add validation attributes that we need on the input fields. AngularJS provides some validation directives such as these; required, pattern, minlength, maxlength, min and max. It also has basic built-in validators for these input types; text, number, url, email and date.
An example on an input field:
<input type="text" name="name" ng-model="vm.input.name" required />- add an error message to be displayed for each validator checking the corresponding property name on input field's $error object in conditional statement like ng-if or ng-show. Properties under $error object with the same names as the validators' names exist for us to use. The properties are on this format; formName.fieldName.$error.builtInValidatorName. For example:
<span ng-show="myForm.name.$error.required == true">* required</span>- on a method that is called in ng-submit, check whether the form is valid using formName.$valid before doing any action
Below is a complete example:
<!-- HTML page -->
<body ng-app="validationExample">
<div ng-controller="MyCtrl as vm">
<form name="myForm" novalidate="" ng-submit="vm.submitted(myForm, vm.input)">
<div>
<input type="text" name="name" ng-model="vm.input.name" required>
<span ng-show="myForm.name.$error.required == true">test: * required</span>
</div>
<button>submit</button>
</form>
</div>
</body>
// JavaScript codes
var myApp = angular.module('validationExample', [])
myApp.controller('MyCtrl', [function () {
var vm = this;
vm.submitted = function(form, input) {
if(form.$valid) {
// post the form
. . .
}
}
} ]);
See these codes on Plunker.Creating Custom Validator
If we would like to create a custom validator, we would need to do these in addition of the above steps:
- create a directive
- on the directive's link function, use the new AngularJS $validators object on ngModel controller to do the validation. We need to create a function property on ngModel.$validators. By doing so, we register the function as a new validation rule. Each time the model changes, the validation rule is invoked. For example:
link: function(scope, element, attributes, ngModel) {
ngModel.$validators.wrongInitial = function(modelValue) {
. . .
};
}
A corresponding property on input field's $error object is also created that can be used for checking validity.- similar like in using built-in validator, we need to add an error message to be displayed by checking the newly created corresponding property on the input field's $error object:
<span ng-show="myForm.name.$error.wrongInitial == true">* must start with letter r</span>
Additional codes to be added from the first example:
<!-- HTML page --> <input type="text" name="name" ng-model="vm.input.name" start-with-r /> <span ng-show="myForm.name.$error.wrongInitial == true">* must start with letter r</span>
// JavaScript codes
myApp.directive("startWithR", function() {
return {
restrict: "A",
require: "?ngModel",
link: function(scope, element, attributes, ngModel) {
ngModel.$validators.wrongInitial = function(modelValue) {
if (modelValue) {
return modelValue.charAt(0).toUpperCase() == 'R';
}
else {
return true;
}
};
}
};
});
See a complete example on Plunker.Using ngMessages to Display Error Messages
In the recent version of AngularJS, started with version 1.3, there is a new feature that we could use to display messages including form error messages. To use this, we need to:
- include a reference to angular-messages.js file in our page
- inject ngMessages module to our AngularJS app
var myApp = angular.module('validationExample', ['ngMessages'])
- if there are only a few fields to be validated, we could specify each error message for each field like this:<!-- use ng-messages with each field's $error object in this format; formName.fieldName.$error -->
<div ng-messages="myForm.name.$error" >
<!-- specify an error message for each validator -->
<span ng-message="required">Name is required!</span>
<span ng-message="wrongInitial">Name must start with letter r</span>
</div>
- however if we know that we are going to repeat this multiple times, we could use a template instead:<!-- create a template by using script tag with type="text/ng-template" and give an Id -->
<script id="errors-template.html" type="text/ng-template" >
<!-- specify an error message for each validator -->
<span ng-message="required">* required!</span>
<span ng-message="wrongInitial">* must start with letter r!</span>
</script>
Then use the template to display error message(s) on each field:<!-- use ng-messages with each field's $error object and ng-messages-include referring to the template Id --> <span ng-messages="myForm.name.$error" ng-messages-include="errors-template.html" />See the complete example on Plunker.
References:
Working with Validators and Messages in AngularJS
Validation in Ionic Framework Apps with ngMessages
2 comments:
Excellent information with unique content and it is very useful to know about the information based on blogs.this is valuable information for learners.thanks
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Great explanation.We can also use ng-pristane ,ng-dirty etc to know the field state.
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