Inject Service in Controller

Now that UserService is ready, let’s inject it into a controller.

What is Dependency Injection?

Dependency injection (DI) lets the framework create and provide dependencies for you.

Manual creation (not recommended)

class UserController {
  async list() {
    const userService = new UserService();
    return userService.getUsers();
  }
}

Midway DI (recommended)

@Controller('/users')
export class UserController {
  @Inject()
  userService: UserService;

  async list() {
    return this.userService.getUsers();
  }
}

Build `UserController`

import { Controller, Get, Query, Param, Inject } from '@midwayjs/core';
import { UserService } from '../service/user.service';

@Controller('/api/users')
export class UserController {
  @Inject()
  userService: UserService;

  @Get('/')
  async list() {
    const users = await this.userService.getUsers();
    return { success: true, data: users };
  }

  @Get('/:id')
  async getOne(@Param('id') id: string) {
    const user = await this.userService.getUserById(parseInt(id));
    if (!user) {
      return { success: false, message: 'User not found' };
    }
    return { success: true, data: user };
  }

  @Get('/search')
  async search(@Query('keyword') keyword: string) {
    const users = await this.userService.searchUsers(keyword || '');
    return { success: true, data: users, count: users.length };
  }
}

Routing recap

Method	Path	Description
GET	`/api/users`	List all users
GET	`/api/users/:id`	Get one user
GET	`/api/users/search?keyword=...`	Search users

Multiple injections

A controller can inject multiple services with @Inject().

Summary

Use @Inject() to request dependencies
Let Midway manage lifecycle and reuse instances
Keep controller thin and delegate logic to service

Create Your First Service

Handle POST Requests

Files

Preparing Environment

npm install
npm run dev