5.module.providers

[eternallycyf]

@Module({
  imports: [PersonModule],
  controllers: [PersonController],
  providers: [PersonService],
  exports: [PersonService],
})

controllers 只能被注入
providers 里可以被注入，也可以注入别的对象

// 1. 
@Module({
  providers: [PersonService],
})
constructor(private readonly personService: PersonService) {}

// 2.
@Inject(PersonService) private personview: PersonService
@Module({
  providers: [PersonService],
})

// 3.
providers: [
  {
    provide: PersonService,
    useClass: PersonService
  }
]
constructor(private readonly personService: PersonService) {}
...

// 4. exports 也要字符串
providers: [
  {
    provide: 'person_service',
    useClass: PersonService
  }
],
exports: ['person_service'],

constructor(@Inject('person_service') private readonly personService) {}

@Inject('person_service') private readonly PersonService: PersonService

// 5.useValue
providers: [
    {
      provide: 'person',
      useValue: {
        name: 'zs',
        age: 12,
      },
    },
],
@Inject('person') private readonly person: {name: string, age: number};
// this.person.name

// 6.useFactory
{
    provide: 'person2',
    useFactory() {
        return {
            name: 'bbb',
            desc: 'cccc'
        }
    }
}
@Inject('person2')
private readonly person2: {name: string, desc: string};

// 7.useFactory 支持通过参数注入别的 provider 
{
  provide: 'person3',
  useFactory(person: { name: string }, appService: AppService) {
    return {
      name: person.name,
      desc: appService.getHello()
    }
  },
  inject: ['person', AppService]
}

// 8. 支持异步
 {
      provide: 'person5',
      async useFactory() {
        await new Promise((resolve) => {
          setTimeout(resolve, 3000);
        });
        return {
          name: 'bbb',
          desc: 'cccc'
        }
      },
    },

// 9.useExisting 指定别名
  {
      provide: 'person4',
      useExisting: 'person2'
 }