directive.js

ng.directive('smGroup', ['$cacheFactory', '$log', function ($cacheFactory, $log) {
    var cache = $cacheFactory('smGroupModelCache');


    function searchAndDestroy(array, target) {
        var index, found;
        if (!Array.isArray(array)) {
            return false;
        }

        // Search for the element
        index = array.indexOf(target);
        found = Boolean(~index);

        if (found) {
            array.splice(index, 1);
        }

        return found;
    }

    function postLink(scope, elm, attrs, ngModelCtrl) {
        if (elm.attr('type').toLowerCase() !== 'checkbox') {
            $log.warn('$element is not of a [type="checkbox"]! @', elm[0]);
        }

        var groupName, groupies, model, destroyers = [];
        groupName = attrs.smGroup;
        if (!groupName) {
            $log.error('Group name is not defined! @', elm[0]);
        }

        groupies = cache.get(groupName) || cache.put(groupName, []);
        model = {model: ngModelCtrl, name: elm.attr('name')};
        groupies.push(model);

        ngModelCtrl.$validators.groupRequired = function($modelValue) {
            var some = groupies.some(function(groupie) {
                if (groupie === model) {
                    return Boolean($modelValue);
                }
                return Boolean(groupie.model.$modelValue);
            });

            return some;
        };

        destroyers.push(
            scope.$on('$destroy', function () {
                destroyers.forEach(function (destroyer) {
                    destroyer();
                });
                searchAndDestroy(groupies, model);
                groupies.forEach(function (groupie) {
                    groupie.model.$validate();
                });
            })
        );
    }

    return {
        restrict: 'A',
        require: 'ngModel',
        link: postLink
    };