nestjs-ioc-example-2

drink.module.ts

import { Module, OnModuleInit } from '@nestjs/common';

import { DrinkService } from './drink.service';
import { DiscoveryModule, DiscoveryService } from "@nestjs/core";
import { DRINK_PROVIDER, DrinkProvider } from "./drink.provider";

@Module({
    imports: [
        DiscoveryModule,
    ],
    providers: [
        DrinkService,
    ],
})
export class DrinkModule implements OnModuleInit {

    constructor(
        private readonly discovery: DiscoveryService,
        private readonly drinkService: DrinkService,
    ) {}

    onModuleInit(): any {
        const wrappers = this.discovery.getProviders();

        const drinkProviders = wrappers
            .filter((wrapper) => wrapper.metatype && Reflect.getMetadata(DRINK_PROVIDER, wrapper.metatype))
            .map((wrapper) => wrapper.instance) as DrinkProvider[];

        drinkProviders.forEach((provider) => this.drinkService.registerProvider(provider));
    }
}

drink.provider.ts

import { SetMetadata } from '@nestjs/common';

import { Drink } from './drink.model';

export const DRINK_PROVIDER = 'DrinkProvider';

export interface DrinkProvider {
    getDrinks(): Promise<Drink[]>;
}

export const DrinkProviderDecorator = () => SetMetadata(DRINK_PROVIDER, true);

spirit.drink.provider.ts

import { Injectable } from '@nestjs/common';

import { DrinkProvider, DrinkProviderDecorator } from '../drink.provider';
import { Drink } from '../drink.model';

@Injectable()
@DrinkProviderDecorator()
export class SpiritDrinkProvider implements DrinkProvider {

    public getDrinks(): Promise<Drink[]> {
        return Promise.resolve([
            {
                name: 'Rum',
                alcoholByVolume: 45,
            },
            {
                name: 'Arrack',
                alcoholByVolume: 50,
            },
            {
                name: 'Cognac',
                alcoholByVolume: 40,
            },
        ]);
    }
}

spirit.module.ts

import { Module } from '@nestjs/common';

import { SpiritDrinkProvider } from './spirit.drink.provider';

@Module({
    providers: [
        SpiritDrinkProvider,
    ],
})
export class SpiritModule {}