我是 Angularjs 和 MongoDB 的新手，我需要从 MongoDB 发送 HTTP 请求，以便自动完成角度材料，当我发送到 git hub API 时，它工作正常，但对于我的数据库，我得到“无法读取未定义的属性‘长度’” 我的客户端控制器

    /*jslint latedef:false*/
(function () {
  'use strict';
  angular
      .module('clientApp')
      .controller('CarnetCtrl', function($http){

        this.querySearch = function(query){
        //for this link work "https://api.github.com/search/users"  
       return$http.get("http://localhost:3000/carnet/export_countries/", {
                params: {
                    q: query
                }
            }).then(function(response){
                return response.data.items;
            });

        };
      });

})();

我的 Mongodb 控制器

    var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var Q = require('q'); // We can now use promises!



//Create Schema
var CarnetExportCountriesSchema = new Schema({


CarnetExportCountriesSchema.statics.getCarnetExportCountries = function(Country_Name_EN) {

    var deferred = Q.defer();

    this.findOne({Country_Name_EN: Country_Name_EN}, function(error, CarnetExportCountries){

        if (error) {

            deferred.reject(new Error(error));
        }
        else {

            deferred.resolve(manufacturers);
        }
    });

    return deferred.promise;
}


CarnetExportCountriesSchema);



module.exports = CarnetExportCountriesSchema;

和 index.js 服务器端：

//Add Middleware necessary for REST API's
app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());
app.use(bodyParser.json({type:'application/vnd.api+json'}));
app.use(methodOverride('X-HTTP-Method-Override'));

//CROS Support
app.use(function(req,res,next){
    res.header('Access-Control-Allow-Origin','*');
    res.header('Access-Control-Allow-Methods','GET,PUT,POST,DELETE');
    res.header('Access-Control-Allow-Headers','Content-Type');
    res.header('("Content-Length", ""+json.length() );');
    next();
});

我的 app.js

  .config(function (
    $routeProvider,
    RestangularProvider
    ) {
    RestangularProvider.setBaseUrl('http://localhost:3000');
    $routeProvider
      .when('/main', {
        templateUrl: 'views/main.html',
        controller: 'MainCtrl',
        controllerAs: 'main'
      })

我的错误：

TypeError: Cannot read property 'length' of undefined
    at hasMatches (angular-material.js:25423)
    at shouldShow (angular-material.js:25415)
    at shouldHide (angular-material.js:25380)
    at setLoading (angular-material.js:25371)
    at angular-material.js:25564
    at handleCallback (angular.js:17010)
    at angular.js:16825
    at processQueue (angular.js:16843)
    at angular.js:16887
    at Scope.$digest (angular.js:17982) "Possibly unhandled rejection: {}"

请帮助我解决这个问题，我搜索并阅读了大约 1 周，但无法解决这个问题