How to add custom validation to an AngularJS form?

Question

I have a form with input fields and validation setup by adding the required attributes and such. But for some fields I need to do some extra validation. How wou

Answer 1

In AngularJS the best place to define Custom Validation is Cutsom directive. AngularJS provide a ngMessages module.

ngMessages is a directive that is designed to show and hide messages based on the state of a key/value object that it listens on. The directive itself complements error message reporting with the ngModel $error object (which stores a key/value state of validation errors).

For custom form validation One should use ngMessages Modules with custom directive.Here i have a simple validation which will check if number length is less then 6 display an error on screen

 

                

                    

                        

                        
Too Short
                    
                
            

Here is how to create custom validation directive

angular.module('myApp',['ngMessages']);
        angular.module('myApp',['ngMessages']).directive('customValidation',function(){
            return{
            restrict:'A',
            require: 'ngModel',
            link:function (scope, element, attr, ctrl) {// 4th argument contain model information 

            function validationError(value) // you can use any function and parameter name 
                {
                 if (value.length > 6) // if model length is greater then 6 it is valide state
                 {
                 ctrl.$setValidity('invalidshrt',true);
                 }
                 else
                 {
                 ctrl.$setValidity('invalidshrt',false) //if less then 6 is invalide
                 }

                 return value; //return to display  error 
                }
                ctrl.$parsers.push(validationError); //parsers change how view values will be saved in the model
            }
            };
        });

$setValidity is inbuilt function to set model state to valid/invalid