Javascript Angular:Ionic.bundle.js:21157 TypeError:Pubnub.publish中的Ionic Pubnub聊天不是函数

我正在使用PubNub Api和ionic平台创建whatsapp应用程序。然而，它带来了一个问题，即ionic.bundle.js:21157 TypeError:PubNub.publish不是一个函数。下面是我的代码。有人能帮我吗

var chat = angular.module('chat', ['pubnub.angular.service']);
   chat.controller('chatController', ['$scope', '$state', '$rootScope',        
   '$stateParams', 'PubNub', '$http', '$ionicScrollDelegate', 
    function($scope, $state, $rootScope, $stateParams, PubNub, $http,    
    $ionicScrollDelegate){
          var nickname = $stateParams.nickname;
          var channel = $stateParams.channel;
          $scope.messageContent = '';
          $scope.messages = [];

          $scope.goBack = function() {
          $state.go('channels',{nickname: nickname, channel: channel}); 
      }

     PubNub.init({
        publish_key:'',
        subscribe_key:'',
        ssl: true,
        nickname: nickname
     });

    $scope.sendMessage = function() {
         if (!$scope.messageContent ||
              $scope.messageContent === '') {
                 return;
         }
    PubNub.publish({
        channel: channel,
        message: {
            content: $scope.messageContent,
            nickname: nickname
        },
        callback: function(m) {
            console.log(m);
        }
    });
    $scope.messageContent = '';
}

PubNub.ngSubscribe({channel: channel});

$rootScope.$on(PubNub.ngMsgEv(channel), function(event, payload) {
    $scope.$apply(function() {
        $scope.messages.push(payload.message);
        $ionicScrollDelegate.scrollBottom();
        console.log(payload.message);
    });

  });
}]);

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要注入的服务的名称是Pubnub而不是Pubnub。

要注入的服务的名称是Pubnub而不是Pubnub。

即使使用正确的依赖项注入（Pubnub），我也会收到相同的错误。即使使用正确的依赖项注入（Pubnub），我也会收到相同的错误