NestJS - Injected service is undefined in the constructor

Question

As per the documentation, I inject a service in a controller's constructor, but it turns out as undefined.

processScraped.controller.ts

import { Controller, Post, Body } from '@nestjs/common'; import { ProcessScrapedService } from "./processScraped.service" console.log(`\nController - ProcessScrapedService = `, ProcessScrapedService) // logs : class ProcessScrapedService { ...... @Controller('processScraped') export class ProcessScrapedController { constructor(private readonly pss: ProcessScrapedService) { console.log(`constructor - pss = `, pss) // logs : undefined (Should not !) console.log(`constructor - this.pss = `, this.pss) // logs : undefined (Should not !) } @Post() async processScraped(@Body() body) { console.log(`processScraped - this.pss = `,this.pss) // logs : undefined (Should not !) return this.pss.processScraped(body) // TypeError: Cannot read property 'processScraped' of undefined } }

So :

The service exists
It's imported and logged correctly as a service after import
When I inject it in my controller, it's undefined.

Maybe the problem is in the service definition?

processScraped.service.ts

import { Component } from '@nestjs/common'; @Component() export class ProcessScrapedService { async processScraped(body) { // Some logic here return } }

... Or maybe in the module?

processScraped.module.ts

import { Module } from '@nestjs/common'; import { ProcessScrapedController } from './processScraped.controller'; import { ProcessScrapedService } from './processScraped.service'; console.log(`\Module - nProcessScrapedService = `, ProcessScrapedService) // logs : class ProcessScrapedService { ...... @Module({ controllers: [ProcessScrapedController], components: [ProcessScrapedService], }) export class ProcessScrapedModule { }

I really can't see what I'm doing wrong here??

EDIT - here are my dependencies :

"dependencies": { "@nestjs/common": "^4.5.9", "@nestjs/core": "^4.5.10", "@nestjs/microservices": "^4.5.8", "@nestjs/mongoose": "^3.0.1", "@nestjs/testing": "^4.5.5", "@nestjs/websockets": "^4.5.8", "@types/mongoose": "^5.0.9", "bluebird": "^3.5.1", "dotenv": "^5.0.1", "elasticsearch": "^14.2.2", "express": "^4.16.3", "mongoose": "^5.0.16", "mongoose-elasticsearch-xp": "^5.4.1", "reflect-metadata": "^0.1.12", "rxjs": "^5.5.6", "shortid": "^2.2.8" }, "devDependencies": { "@types/node": "^8.0.0" }

and my tsconfig.json :

{ "compilerOptions": { "target": "ES2017", "module": "commonjs", "lib": [ "dom", "es2017" ], "outDir": "../../dist/server", "removeComments": true, "strict": true, "noImplicitAny": false, "typeRoots": [ "node_modules/@types" ], "types": [ "node" ], "experimentalDecorators": true } }

What version are you using? Could you share your tsconfig file? — Kamil Myśliwiec
– Kamil Myśliwiec, Commented May 1, 2018 at 8:03
@KamilMyśliwiec Alright, I have updated my question with my dependencies and tsconfig — Jeremy Thille
– Jeremy Thille, Commented May 1, 2018 at 18:06

Kamil Myśliwiec · Accepted Answer · 2018-05-01 18:32:53Z

59

The "emitDecoratorMetadata": true is missing in your tsconfig.json file.

answered May 1, 2018 at 18:32

Kamil Myśliwiec

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4 Comments

Jeremy Thille Over a year ago

Oh wow O_o I have no idea what this is, but it fixed the problem. I would never have found that by myself. Thanks Kamil, you're the man.

djnose Over a year ago

had the same (similar) issue today, had to add the following to my tsconfig.json "experimentalDecorators": true, "declaration": true, "removeComments": true, "emitDecoratorMetadata": true

Franco Over a year ago

You saved my day, weird it's not included in the default nest new project template

William Neely Over a year ago

Because of an issue with Jest test coverage in Angular, I did a global remove of emitDecoratorMetadata since Angular no longer needs it. Which also removed from nest which does still need the flag.

Georgi Stoimenov · Accepted Answer · 2019-02-10 08:02:47Z

59

Just stumbled across the same issue in one of my providers - the problem was that I forgot to annotate the provider with an @Injectable() decorator after I have added it to the respective module.

answered Feb 10, 2019 at 8:02

Georgi Stoimenov

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2 Comments

Andrew Radulescu Over a year ago

Haha, I love when this happens. It's like a checklist with possible adjacent problems. Thanks!

crice1988 Over a year ago

Thank you so much for this. You just saved me from spinning my wheels for hours.

Rohit Gupta · Accepted Answer · 2022-03-21 20:19:20Z

12

One of my providers was scoped with REQUEST scope. I removed it and it resolved more errors than one.

answered Mar 21, 2022 at 20:19

Rohit Gupta

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2 Comments

Ivan Stanev Over a year ago

This should be upvoted higher

danthedaniel Over a year ago

Also had an issue using @Inject(REQUEST) on a provider constructor elsewhere in my code.

Solomon ABOYEJI · Accepted Answer · 2022-07-15 09:35:01Z

Recently faced the same issue in a service that depends on a service in another module. While everything in the answers above is already in place, annotating the imported service with Inject(ImportedService) at the constructor solved the problem.

Pierre Olivier Tran · Accepted Answer · 2022-07-28 09:46:55Z

Sometimes, you'll need to scope your request, but doing so might result in crashing tests. Make sure you override the scope in your tests, using the Reflect trick:

 Reflect.defineMetadata( 'scope:options', { scope: Scope.DEFAULT }, YourService, );

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