CODEWITHSUNDEEP
typescriptdependency-injectiondependenciesinversifyjs
apostrophedottilde
apostrophedottilde

Reputation: 877

Inversify dependency injection not injecting dependencies into constructor

I have followed the guide on npm and github for inversify to configure dependency injection in my Typescript project.

I have a controller, a service and a router. The service is injected into the controller via constructor injection and the controller is pulled from the dependency injection container directly inside the router.

I get an error that 'Cannot read property 'listingService' of undefined'.

It seems the controller is accessed but for some reason when I try to access the service i find it is undefined.

Can anybody please enlighten me as to what the problem is?

The relevant skeleton code necessary to provide my working is as follows:

// ts.config.json
{
  "compileOnSave": true,
  "compilerOptions": {
    "target": "es5",
    "lib": ["es6"],
    "types": ["reflect-metadata"],
    "module": "commonjs",
    "moduleResolution": "node",
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  },
  "include": ["typings.d.ts", "server/**/*.ts"],
  "exclude": ["node_modules"]
}

// TYPES.ts
const TYPES = {
    ListingController: Symbol.for("ListingController"),
    ListingService: Symbol.for("ListingService")
};
export { TYPES };



// inversify.config.ts
import "reflect-metadata";
import { Container } from "inversify";
import {TYPES} from "./Types";
import {ListingController} from "./interfaces/ListingController";
import {ListingControllerImpl} from "../controllers/ListingControllerImpl";
import {ListingService} from "./interfaces/ListingService";
import {ListingServiceImpl} from "../services/ListingServiceImpl";

const myContainer = new Container();
myContainer.bind<ListingController>(TYPES.ListingController).to(ListingControllerImpl);
myContainer.bind<ListingService>(TYPES.ListingService).to(ListingServiceImpl);
export { myContainer };



// router.ts
import * as express from 'express';
const app = express();
import {myContainer} from "../d.i./inversify.config";
import {TYPES} from "../d.i./Types";
import {ListingController} from "../d.i./interfaces/ListingController";
const listingController = myContainer.get<ListingController>(TYPES.ListingController);
app.post('/', listingController.create);
export default app;



export interface ListingController {
    create(req: Request, res: Response): void;
}



export interface ListingService {
    create(body: any, id: string): Promise<any>;
}



@injectable()
export class ListingControllerImpl implements ListingController { 
    public listingService: ListingService;

    constructor()

    constructor(@inject(TYPES.ListingService) listingService: ListingService) {
        this.listingService = listingService;
    }

    public create(req: Request, res: Response): void {
       this.listingService.create();
    }
}



@injectable()
export class ListingServiceImpl implements ListingService {
    constructor()

    constructor() {
        
    }

    public all(uid: string, page: number, size): Promise<any> {
     //
    }

    public byId(id: string, uid: string): Promise<any> {
      //
    }

    public create(body: any, userId: string): Promise<any> {
        // do something
    }
}

Upvotes: 0

Views: 3060

Answers (1)

apostrophedottilde
apostrophedottilde

Reputation: 877

Ok, so I have found the problem.

The issue was not actually anything to do with the dependency injection choice or implementation, but in fact was a slight misunderstanding I had of the closure property.

When I attempted to invoke the listingService's create method from the controller using this.listingService.create() 'this' was not pointing at an instantiation of the controller class.

By using instance function notation I gained access to the scope I was expecting and can now invoke the service method without any problems.

public create = (req: Request, res: Response, next: NextFunction): void => {
    this.listingService.create();
});

I hope this can help somebody.

Upvotes: 3

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