How to intercept value binding by ng-model directive

I found that custom directive is a good approach to intercept binding. Let declare a directive like this:

module.directive('banknumber', function () {
        return {
            require: 'ngModel',
            link: function ($scope, $element, $attrs, modelCtrl) {
                modelCtrl.$formatters.push(function (inputValue) {
                    var modelValue = modelCtrl.$modelValue;
                    var bkno = (modelValue == null) ? '' : modelValue.split(',')[0];

                    return bkno;
                });

                modelCtrl.$parsers.push(function (inputValue) {
                    var modelValue = modelCtrl.$modelValue;
                    var bankName = (modelValue == null) ? '' : modelValue.split(',')[1];

                    return modelCtrl.$viewValue + ',' + bankName;
                });
            }
        };
    });

apply to input and it's done:

<input name="bank_number" ng-model="bankInfo" banknumber/>