Nest.js inject service into plain typescript class

Question

I have a NestJS App and I have a Class where the app generates multiple instances from. Inside that class I need to access a service method but I dont know how to inject a service into a plain class.

This is the service I want to use inside the class "Stream"

import { Injectable } from '@nestjs/common';
import * as technicalindicators from 'technicalindicators';
import { CandleIndex } from 'src/utils/CandleIndex';
import * as ccxt from 'ccxt';
@Injectable()
export class AnalysisService {
  async RSI(ohlcv: ccxt.OHLCV[], period: number) {
    const close = ohlcv.map((candle) => candle[CandleIndex.CLOSE]);
    const result = technicalindicators.rsi({ values: close, period: period });
    return result;
  }
}

import { AnalysisService } from './analysis.service';
import { Module } from '@nestjs/common';

@Module({
  imports: [],
  controllers: [],
  providers: [AnalysisService],
  exports: [AnalysisService],
})
export class AnalysisModule {}

Here is the class I want to get access to the analysis service. The class is a normal typescript class, its not part of any module.

export class Stream {
  private exchange: ccxt.Exchange;
  private market: ccxt.Market;
  private timeframe: string;
  private ohlcv_cache: ccxt.OHLCV[];
  private createdAt: Date;
  private stream;
  @Inject(AnalysisService)
  private readonly analysisService: AnalysisService;
  constructor(exchange: ccxt.Exchange, market: ccxt.Market, timeframe: string) {
    this.exchange = exchange;
    this.market = market;
    this.timeframe = timeframe;
    this.createdAt = new Date();
    this.initialize();
    console.log(this.analysisService);
  }
  }

When I do this and call a method of the analysis service inside of the Stream class, analysisService is undefined.

I have a service which has an Array of Streams[] Class. Inside the same service they get created by pushing new Instances of Stream into the array. — BitQueen
– BitQueen, Commented Nov 22, 2022 at 15:08
yes. They are just simple es6 classes I create by /POST requests which then get stored inside stream.service class inside an array of Type Stream[] — BitQueen
– BitQueen, Commented Nov 22, 2022 at 15:17

Jackie McDoniel · Accepted Answer · 2022-11-22 15:42:29Z

2

As you're calling new Stream() yourself, Nest will do no injection for you. You'd need to either pass the AnalysisService instance yourself, or you'd need to create a setter for that property before running any methods that need the AnalysisService.

answered Nov 22, 2022 at 15:42

Jackie McDoniel

71.7k9 gold badges191 silver badges196 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

BitQueen Over a year ago

you basically make the Constructor of Stream have a param of analysisService and then on Object creation pass the service instance to the Object constructor?

Jackie McDoniel Over a year ago

Yeah. Because if you handle the creation of the class, Nest won't do any injection for you

Collectives™ on Stack Overflow

Nest.js inject service into plain typescript class

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related