三、Providers

说明

Providers 在nest内是服务或者功能的提供则，nest内很多类都通过privider实现，如service, repository, factory, helper，通过构造函数注入，使用@Injectable()装饰器注释类

使用

简单使用

• user.service.ts

import { Injectable } from '@nestjs/common';
import { CreateUserDto } from './dto/create-user.dto';
import { UpdateUserDto } from './dto/update-user.dto';

@Injectable()   //添加装饰器
export class UserService {
  create(createUserDto: CreateUserDto) {
    return 'This action adds a new user';
  }

  findAll() {
    return `This action returns all user`;
  }

  findOne(id: number) {
    return `This action returns a #${id} user`;
  }

  update(id: number, updateUserDto: UpdateUserDto) {
    return `This action updates a #${id} user`;
  }

  remove(id: number) {
    return `This action removes a #${id} user`;
  }
}

• 定义user module,user.module.ts

import { Module } from '@nestjs/common';
import { UserService } from './user.service';
import { UserController } from './user.controller';

@Module({
  controllers: [UserController],
  providers: [
              UserService,
              { provide: "test",useClass: UserService},
              {provide: "ds",useValue: ['TB', 'PDD', 'JD']} //自定义注入值
            ],
  exports: [UserService,{ provide: "test",useClass: UserService}, 
  {provide: "ds",useValue: ['TB', 'PDD', 'JD']}]    //如果想暴露给其他服务使用
})
export class UserModule {}

• app.module.ts引入模组

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { UserModule } from './user/user.module';

@Module({
  imports: [UserModule],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

• app.controller.ts使用service

import { Controller, Get,Inject } from '@nestjs/common';
import { AppService } from './app.service';
import { UserService } from './user/user.service';

@Controller()
export class AppController {
  constructor(private readonly appService: AppService,
      private readonly userService: UserService,
      @Inject("test") private readonly service1: UserService,
      @Inject("ds") private list1:string[] ) {}

  @Get()
  getHello(): string {
    return this.appService.getHello();
  }
  @Get('findAll')
  findAllUsers(): string{
    return this.userService.findAll()+' [app]';
  }
  @Get('findOne')
  findOne(): string{
    return this.service1.findOne(1)+' [app]';
  }
  
  @Get('list')
  list(): string[]{
    return this.list1;
  }
  
}

其他

如果服务 之间有相互的依赖 或者逻辑处理 可以使用 useFactory

import { Module } from '@nestjs/common';
import { UserService } from './user.service';
import { UserService2 } from './user.service2';
import { UserService3 } from './user.service3';
import { UserController } from './user.controller';
 
@Module({
  controllers: [UserController],
  providers: [{
    provide: "Xiaoman",
    useClass: UserService
  }, {
    provide: "JD",
    useValue: ['TB', 'PDD', 'JD']
  },
    UserService2,
  {
    provide: "Test",
    inject: [UserService2],
    useFactory(UserService2: UserService2) {
      return new UserService3(UserService2)
    }
  }
  ]
})
export class UserModule { }

• 注入代码如下：

constructor(@Inject('Test') private readonly Test: any)

• 异步模式，useFactory 返回一个promise 或者其他异步操作

import { Module } from '@nestjs/common';
import { UserService } from './user.service';
import { UserService2 } from './user.service2';
import { UserService3 } from './user.service3';
import { UserController } from './user.controller';
 
@Module({
  controllers: [UserController],
  providers: [{
    provide: "Xiaoman",
    useClass: UserService
  }, {
    provide: "JD",
    useValue: ['TB', 'PDD', 'JD']
  },
    UserService2,
  {
    provide: "Test",
    inject: [UserService2],
    useFactory(UserService2: UserService2) {
      return new UserService3(UserService2)
    }
  },
  {
    provide: "sync",
    async useFactory() {
      return await  new Promise((r) => {
        setTimeout(() => {
          r('sync')
        }, 3000)
      })
    }
  }
  ]
})
export class UserModule { }