Extracting json array from http response

I'm new to AngularJS for a project and I'm trying to extract a json array from a http response to use in a list.

The response looks like this:

{"DFH0XCMNOperationResponse":{"ca_return_code":0,"ca_inquire_request":{"ca_last_item_ref":150,"ca_item_count":15,"ca_cat_item":[{"ca_cost":"002.90","in_stock":119,"ca_description":"Ball Pens Black 24pk","on_order":0,"ca_department":10,"ca_item_ref":10},{"ca_cost":"002.90","in_stock":6,"ca_description":"Ball Pens Blue 24pk","on_order":50,"ca_department":10,"ca_item_ref":20}],"ca_list_start_ref":0},"ca_response_message":"+15 ITEMS RETURNED","ca_request_id":"01INQC"}}

The code for the resource and request looks like this:

.factory('getCatalog', ['$resource', function($resource){
    return $resource('catalogmanagertest/v1/apps/bca45894-92f7-49dc-ae54-b23b89ab6c73/catalog', {}, {query: {method:'POST'}});
}]);

And the controller code relevant looks like this:

angular
.module('catalogController', ['ngMaterial', 'ngResource'])
.controller('catalogController', ['$scope', 'getCatalog', 'catalog', function($scope, getCatalog, catalog) {
    $scope.debug = getCatalog.query(); // set scope catalog to array from zOS
    $scope.catalog = catalog.ca_cat_item;
    $scope.message = "This is a test order message";
this.tiles = buildGridModel({
        icon : "avatar:svg-",
        title: "",
        cost: "€",
        background: "",
        stock: ""
    });
    function buildGridModel(tileTmpl){
        var it, results = [ ];

        var tmp = $scope.debug.DFH0XCMNOperationResponse.ca_inquire_request.ca_cat_item;
        console.log(tmp);

The next to last line is what I'm having trouble with. How do extract the expected array? I get the newbie error when I do the console.log:

TypeError: Cannot read property 'ca_inquire_request' of undefined