The Angular TypeScript service encounters an undefined issue

Here is an example of my Angular TypeScript Interceptor:

export module httpMock_interceptor {
  export class Interceptor  {
      static $inject: string[] = ['$q'];
      constructor(public $q: ng.IQService) {}
       public request(config: any) {
         console.log(this);
       }
     }
   }

In this module, I am registering the interceptor as a service.

import {httpMock_interceptor as interceptor} from './httpMock.interceptor';
var httpMock: ng.IModule = angular.module("httpMockTs", []);
httpMock.service("httpMockInterceptor",interceptor.Interceptor);
httpMock.config.$inject = ['$httpProvider'];
httpMock.config(['$httpProvider', function ($httpProvider:  ng.IHttpProvider) {
$httpProvider.interceptors.unshift('httpMockInterceptor');
}]);

After initializing, the interceptor constructor sets the $q service. However, when it reaches the request method and uses the this keyword, the browser throws an error saying that this is undefined. Can anyone point out where I might be making a mistake?

And here is the transpiled code for the interceptor:

export var httpMock_interceptor;
 (function (httpMock_interceptor) {
   class Interceptor {
    constructor(_q) {
        this._q = _q;
    }
    request(config) {
        console.log(this);
    }
   }
Interceptor.$inject = ['$q'];
httpMock_interceptor.Interceptor = Interceptor;
})(httpMock_interceptor || (httpMock_interceptor = {}));

This is the module:

import { httpMock_interceptor as interceptor } from './httpMock.interceptor';
var httpMock = angular.module("httpMockTs", []);
httpMock.service("httpMockInterceptor", interceptor.Interceptor);
httpMock.config.$inject = ['$httpProvider'];
httpMock.config(['$httpProvider', function ($httpProvider) {
    $httpProvider.interceptors.unshift('httpMockInterceptor');
}]);
export { httpMock };

Answer №1

Consider implementing an arrow function that holds onto a reference to the parent object or acting as an interceptor:

private fetchData = (params: any) => {
  console.log(this);
}

To learn more, visit: How Lambdas use 'this' @ http://www.typescriptlang.org/Handbook#functions

Answer №2

The information provided in the documentation suggests that the interceptor must be a function that generates an object with specific attributes such as request. Based on this, my assumption is that the request function is invoked directly without any necessity for a this reference.

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