NestJS Services 詳解：サービスの作成と注入及びビジネスロジックの管理

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import { Injectable } from "@nestjs/common";
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@Injectable()
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export class UsersService {
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  private readonly users = [];
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  findAll() {
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    return this.users;
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  }
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  findOne(id: string) {
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    return this.users.find((user) => user.id === id);
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  }
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  create(user) {
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    this.users.push(user);
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  }
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  update(id: string, user) {
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    const existingUser = this.findOne(id);
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    if (existingUser) {
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      Object.assign(existingUser, user);
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    }
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  }
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  remove(id: string) {
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    const index = this.users.findIndex((user) => user.id === id);
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    if (index !== -1) {
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      this.users.splice(index, 1);
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    }
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  }
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}

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import {
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  Controller,
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  Get,
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  Post,
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  Put,
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  Delete,
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  Param,
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  Body,
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} from "@nestjs/common";
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import { UsersService } from "./users.service";
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@Controller("users")
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export class UsersController {
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  constructor(private readonly usersService: UsersService) {}
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  @Get()
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  findAll() {
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    return this.usersService.findAll();
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  }
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  @Get(":id")
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  findOne(@Param("id") id: string) {
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    return this.usersService.findOne(id);
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  }
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  @Post()
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  create(@Body() createUserDto: CreateUserDto) {
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    return this.usersService.create(createUserDto);
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  }
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  @Put(":id")
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  update(@Param("id") id: string, @Body() updateUserDto: UpdateUserDto) {
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    return this.usersService.update(id, updateUserDto);
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  }
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  @Delete(":id")
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  remove(@Param("id") id: string) {
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    return this.usersService.remove(id);
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  }
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}

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import { Injectable } from "@nestjs/common";
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import { User } from "./user.entity";
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@Injectable()
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export class UsersService {
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  private readonly users: User[] = [];
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  findAll(): User[] {
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    return this.users;
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  }
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  findOne(id: string): User {
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    return this.users.find((user) => user.id === id);
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  }
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  create(user: User) {
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    this.users.push(user);
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  }
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  update(id: string, user: User) {
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    const existingUser = this.findOne(id);
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    if (existingUser) {
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      Object.assign(existingUser, user);
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    }
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  }
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  remove(id: string) {
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    const index = this.users.findIndex((user) => user.id === id);
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    if (index !== -1) {
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      this.users.splice(index, 1);
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    }
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  }
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}

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import { Injectable } from "@nestjs/common";
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@Injectable()
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export class AuthService {
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  validateUser(username: string, password: string): boolean {
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    // 仮定としてここにユーザーリストがあります
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    const users = [{ username: "test", password: "password" }];
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    const user = users.find(
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      (user) => user.username === username && user.password === password,
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    );
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    return !!user;
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  }
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}

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import { Injectable, HttpService } from "@nestjs/common";
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import { map } from "rxjs/operators";
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@Injectable()
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export class ExternalApiService {
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  constructor(private readonly httpService: HttpService) {}
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  fetchData() {
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    return this.httpService
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      .get("https://api.example.com/data")
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      .pipe(map((response) => response.data));
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  }
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}