I am trying to build a simple http app using node-express.
Issue when setting up routes, the constructor of the MyRouter class has this but it's lost in the getRoutes() function.
class Main {
public async run(): Promise<void> {
const myRouter = new MyRouter(this.config);
// this.server is express() during construct
this.server.use("/v1", myRouter.getRoutes);
await this.server.listen(this.config.rest.port);
}
}
class MyRouter {
private router: express.Router;
constructor(private config: any) {
this.router = express.Router();
console.log(this); // Prints the whole Router object!
}
public getRoutes(): express.Router {
console.log(this); // = "undefined" !
this.router.use("/test", otherClass.getRoutes);
return this.router;
}
}
Why is this?
The value of this depends not on where it is defined but by how a function is called. You did this:
this.server.use("/v1", myRouter.getRoutes);
This is equivalent to:
var tmp = myRouter.getRoutes;
this.server.use("/v1", tmp); // `this` will refer to the global object
There are two solutions. Either wrap it in an anonymous function to retain the object that calls the function:
this.server.use("/v1", function(){return myRouter.getRoutes()});
Or use .bind()
this.server.use("/v1", myRouter.getRoutes.bind(myRouter));
Related
I'm using Express into a TypeScript project and I have the following situation
This is my route file
...
import findAllUsersFactory from "src/factory/FindAllUsers";
routes.get("/users", findAllUsersFactory().handle);
...
This is the factory where I do a sequence of injections
const findAllUsersFactory = () => {
const findAllUserRepository = new PrismaUsersRepository();
const findAllUsersBusiness = new FindAllUsersBusiness(findAllUserRepository);
const findAllUsersController = new FindAllUsersController(findAllUsersBusiness);
return findAllUsersController;
};
This is my Controller
class FindAllUsersController {
constructor(private findUserBusiness: FindAllUsersBusiness) { }
async handle(request: Request, response: Response) {
const allUsers = await this.findUserBusiness.execute();
return response.status(200).send({ allUsers });
}
}
And finally my Business
class FindAllUsersBusiness {
constructor(private usersRepository: IUsersRepository) {}
async execute() {
return this.usersRepository.findAll();
}
}
The problem is that I'm getting an error "Cannot read property 'execute' of undefined" because the findUserBusiness into handle function is undefined. And what I can't understand is that if I change my route to
routes.get("/users", (request, response) => {
findAllUsersFactory().handle(request, response);
});
it works
I've tried to log the functions, but I can say why findUserBusiness is undefined since it came from the constructor, and since the handle functions came from an instance of FindAllUsersController it should have it "defined"
You need to make some adjustments in order to adapt your factory to the way router.get expects its parameters.
const findAllUsersFactory = (req, res) => {
const findAllUserRepository = new PrismaUsersRepository();
const findAllUsersBusiness = new FindAllUsersBusiness(findAllUserRepository);
const findAllUsersController = new FindAllUsersController(findAllUsersBusiness);
return findAllUsersController.handle(req, res)
};
Then in your router you need to do the following:
routes.get("/users", findAllUsersFactory);
I want to share a server between all my tests, to do this I create the file server-environment.js
const NodeEnvironment = require('jest-environment-node')
const supertest = require('supertest')
//A koa server
const { app, init } = require('../src/server')
class ServerEnvironment extends NodeEnvironment {
constructor(config, context) {
super(config, context)
this.testPath = context.testPath
}
async setup() {
await init
this.server = app.listen()
this.api = supertest(this.server)
this.global.api = this.api
}
async teardown() {
this.server.close()
}
}
module.exports = ServerEnvironment
The thing is that I want to mock some middleware that the servers routes use but I can't really find a way to do that. If I try to declare jest.mock anywhere in the file I get the error that jest isn't defined. If I mock the function in the actual test file the global wouldn't make use of it. Not sure if something like this would be possible to do with Jest?
I had a same issue and solved it by adding setupFilesAfterEnv.
jest.config.js:
module.exports = {
...
setupFilesAfterEnv: [
'./test/setupMocks.js'
]
...
};
test/setupMocks.js
jest.mock('path/to/api', () => global.api);
I was trying to create an endpoint in node.js, more specifically in express
but I am not sure why I can't access userService variable when requesting from a client.
I've gotten Cannot read property 'userService' of undefined, but when i move ServicesFactory.getInstance().getUserService() inside the signUp function it works?!
I am guessing that node.js garbage collects it due to it's not being used until the user make a request.
export class UserApi implements WebEndpoint {
router: Router
userService = ServicesFactory.getInstance().getUserService()
constructor() {
this.router = Router()
this.router.post('/signup', this.signUp)
}
signUp(req: Request, res: Response): void {
const user: User = req.body
this.userService.signUp(user)
res.send("Successfully registered")
}
}
I found the problem, so basically I am a noob.
consider this example
class a {
constructor() {
this.a1 = 'hello';
}
greet(){
const greeting = `${this.a1} dude!`;
console.log(greeting);
};
}
class b {
b1 = new a();
constructor() {
this.b1.greet.call();
}
}
new b();
Now it wouldn't run, because b class called greet method with a new context, the same with express when you provide a function as a handler on an Express endpoint it will be called with a new set of context (read:this) that's why this.userService in my code above won't work because there is no userService property in the context provided by Express.
The solution is simple. Arrow function.
signUp = (req: Request, res: Response): void => {
const user: User = req.body
this.userService.signUp(user)
res.send("Successfully registered")
}
Now the function will inherit it's class's context.You can refer to this for more detail answer.
I'm writing my own implementation of middleware for a socket system. I've read through the source code of Laravel's middleware and some documentation on ExpressJS's implementation for inspiration.
However, I'm getting stuck on passing the data from one middleware handler to another.
I wrote a very basic example below. The output should be 4 but I don't know how to pass the output from one handler to the other. I'm guessing by setting a temporary variable, but I'm not sure how performant that is.
let each = require('lodash/each')
class Middleware {
constructor() {
this.handlers = [
function (data) {return data + 1},
function (data) {return data + 2}
]
}
}
class Router {
constructor() {
this.middleware = new Middleware
}
route(data) {
each(this.middleware.handlers, function(handler) {
handler(data) // no idea what to do here
})
}
}
class Socket {
constructor() {
this.router = new Router
}
write(data) {
return this.router.route(data)
}
}
let router = new Router
console.log(socket.write(1)) // should be 4
Change the route function inside Router class as following and the result of socket.write(1) will be 4:
class Router {
constructor() {
this.middleware = new Middleware
}
route(data) {
each(this.middleware.handlers, function (handler) {
data = handler(data)
})
return data
}
}
I'm new in typescript. In my node-express app, I want to call public function. But this is always undefined, so when I call public function, it throw always error. My code is given below:
app.ts
import * as express from 'express';
import User from './user/ctrl';
class App {
public express: express.Application;
constructor() {
this.express = express();
this.routes();
}
private routes():void {
let router = express.Router();
router.get('/', User.index);
this.express.use('/', router);
}
}
export default new App().express;
./user/ctrl.ts
class User {
public demo:string;
constructor() {
this.demo = "this is text";
}
public infox() {
console.log("demoo test : ", this.demo);
}
public index(req:any, res:any) {
console.log(this) // output: undefined
this.infox(); // throw an error.
}
}
const user = new User();
export default user;
Server run at port 3000.
Any suggestion??
When you passed a reference the User.index function, the this inside it will change based on how it is called. Or when strict mode is on this will be undefined.
Change router.get('/', User.index); to router.get('/', (req, res) => User.index(req, res));. Notice that User.index is wrapped inside an arrow function which captures the correct this when User.index is called.
See red flags for this in TypeScript