AngularJS: $_POST e $_FILES

// Envia os dados com o upload
$http({
    method: 'POST',
    url: ,
    headers: { 'Content-Type': undefined },
    transformRequest: function(data) {
        var formData = new FormData();
        formData.append("post", angular.toJson(data.post));

        // Agora add os arquivos
        for (var i = 0; i < data.files.length; i++) {
            formData.append("file" +i, data.files[i]);
        }
        return formData;
    },
    data: {post: $scope.post, files: $scope.files}
})
.success(function( data, status, headers, config) {

})

/* Diretiva */
(function() {
    'use strict';

    angular
        .module('app')
        .directive('fileUpload', fileUpload);

    function fileUpload() {

        return {
            scope: true,        //create a new scope
            link: function (scope, el, attrs) {
                el.bind('change', function (event) {
                    var files = event.target.files;
                    //iterate files since 'multiple' may be specified on the element
                    for (var i = 0;i<files.length;i++) {
                        //emit event upward
                        scope.$emit("fileSelected", { file: files[i] });
                    }
                });
            }
        };
    }
})();