Service

• Create service class

    nest g service cats

Example

    import { Injectable } from '@nestjs/common';
    import { Cat } from './interfaces/cat.interface';

    @Injectable()
    export class CatsService {
        private readonly cats: Cat[] = [];

        create(cat: Cat) {
            this.cats.push(cat);
        }

        findAll(): Cat[] {
            return this.cats;
        }
    }

• The only new feature is that it uses the @Injectable() decorator.
• The @Injectable() decorator attaches metadata, which declares that CatsService is a class that can be managed by the Nest IoC container.

Usage

    import { Controller, Get, Post, Body } from '@nestjs/common';
    import { CreateCatDto } from './dto/create-cat.dto';
    import { CatsService } from './cats.service';
    import { Cat } from './interfaces/cat.interface';

    @Controller('cats')
    export class CatsController {
        
        constructor(private catsService: CatsService) {}

        @Post()
        async create(@Body() createCatDto: CreateCatDto) {
            this.catsService.create(createCatDto);
        }

        @Get()
        async findAll(): Promise<Cat[]> {
            return this.catsService.findAll();
        }
    }