I recently embarked on a new project utilizing Express with TypeScript and I am currently in the process of setting up a DI container with InversifyJS. The scenario is quite simple, involving only 1 route and controller. Here are the key files I have created:
controller\projects\projects.controller
import { inject, injectable } from "inversify";
import "reflect-metadata";
import { IProjectService } from "../../services/projects/interface/IProjectService";
import { TYPES } from "../../services/projects/types";
@injectable()
class ProjectController {
private _processService: IProjectService;
constructor(@inject(TYPES.IProjectService) projectService: IProjectService) {
this._processService = projectService;
}
public getProjects(): string {
return this._processService.getProject();
}
}
export { ProjectController };
services\projects\imp\ProjectService.ts
import { injectable } from "inversify";
import "reflect-metadata";
import { IProjectService } from "../interface/IProjectService";
@injectable()
class ProjectService implements IProjectService {
getProject(): string {
return "Project A";
}
}
@injectable()
class AnotherProjectService implements IProjectService {
getProject(): string {
return "Project B";
}
}
export { ProjectService, AnotherProjectService };
services\projects\interface\IProjectService.ts
export interface IProjectService {
getProject(): string;
}
routes\projects.ts In this section, I request an instance of the ProjectController from the container as expected. However, the private instance of IProjectService within it appears to be undefined at runtime.
import { myContainer } from "../../inversify.config";
import { ProjectController } from "../controllers/projects/projects.controller";
import { CONTROLLERS_TYPES } from "../controllers/types";
import * as express from "express";
const router = express.Router();
const pc = myContainer.get<ProjectController>(
CONTROLLERS_TYPES.ProjectController
);
router.get("/", pc.getProjects);
export default router;
root\inversify.config.ts
import { Container } from "inversify";
import { TYPES } from "./src/services/projects/types";
import { IProjectService } from "./src/services/projects/interface/IProjectService";
import { ProjectService } from "./src/services/projects/imp/ProjectService";
import { CONTROLLERS_TYPES } from "./src/controllers/types";
import { ProjectController } from "./src/controllers/projects/projects.controller";
const myContainer = new Container();
myContainer
.bind<ProjectController>(CONTROLLERS_TYPES.ProjectController)
.to(ProjectController);
myContainer.bind<IProjectService>(TYPES.IProjectService).to(ProjectService);
export { myContainer };
controllers\types.ts
const CONTROLLERS_TYPES = {
ProjectController: Symbol.for("ProjectController"),
};
export { CONTROLLERS_TYPES };
services\projects\types.ts
const TYPES = {
IProjectService: Symbol.for("IProjectService"),
};
export { TYPES };
Finally, let's take a look at my main:
import projectRoutes from "./routes/projects";
import express from "express";
const app = express();
app.get("/", function (req, res) {
res.send("Hello World");
});
app.use("/api/projects", projectRoutes);
console.log("Listening on port 3000");
app.listen(3000);
When attempting to call the get method of the controller, I encounter the following error:
Cannot read properties of undefined (reading '_processService')This suggests that the initialization of the _processService variable in the controller was not successful. Any insights on what might be missing?