NestJS：无法为拥有接口的子模块提供实例答案

【问题标题】：NestJS : cannot provide an instance to child module owning the interfaceNestJS：无法为拥有接口的子模块提供实例
【发布时间】：2021-05-05 19:20:49
【问题描述】：

我尝试将 NestJs 模块的控制器模块与域模块分离（根据干净架构原则），以便依赖项仅流向域。我不明白如何让它工作，没有注入 repo 接口的实现（嵌套开始时出错）。

这是模块结构：

AppModule     ->     CommunityControllerModule     ->     DomainModule
                       (provides repoImpl                   (has service requiring an unknown
                        by token)                            concrete repo interface impl)

社区控制器模块：

import { DomainModule } from 'libs/domain/src';
import { Module } from '@nestjs/common';
import { CommunityController } from './community.controller';
import { CommunityRepositoryImpl } from './community.repository';

@Module({
  imports: [DomainModule, CommunityRepositoryImpl],
  controllers: [CommunityController],
  exports: [CommunityRepositoryImpl],
  providers: [
    {
      provide: 'CommunityRepository',
      useClass: CommunityRepositoryImpl,
    },
  ],
})
export class CommunityControllerModule {}

域模块：

import { Module } from '@nestjs/common';
import { CommunityService } from './community.service';

@Module({
  providers: [CommunityService],
  exports: [CommunityService],
})
export class DomainModule {}

注入失败的社区服务：

import { HttpException, HttpStatus, Inject, Injectable } from '@nestjs/common';
import { CommunityRepository } from './community.repo';

@Injectable()
export class CommunityService {
  
  constructor(
    @Inject('CommunityRepository') private repo: CommunityRepository,
  ) {}
}

输出的错误：

> nest start

webpack 5.28.0 compiled successfully in 8218 ms
[Nest] 7204   - 2021-05-05 20:52:05   [NestFactory] Starting Nest application...
[Nest] 7204   - 2021-05-05 20:52:05   [InstanceLoader] CommunityRepositoryImpl dependencies initialized +49ms
[Nest] 7204   - 2021-05-05 20:52:05   [ExceptionHandler] Nest can't resolve dependencies of the CommunityService (?). Please make sure that the argument CommunityRepository at index [0] is available in the DomainModule context.

Potential solutions:
- If CommunityRepository is a provider, is it part of the current DomainModule?
- If CommunityRepository is exported from a separate @Module, is that module imported within DomainModule?
  @Module({
    imports: [ /* the Module containing CommunityRepository */ ]
  })

【问题讨论】：

标签： nestjs clean-architecture

【解决方案1】：

我错过了将 DomainModule 设置为 dynamic module。

域模块变为：

import { DynamicModule, Module } from '@nestjs/common';
import { CommunityService } from './community.service';

@Module({})
export class DomainModule {
  static register(repoImpl): DynamicModule {
    return {
      module: DomainModule,
      imports: [repoImpl],
      providers: [
        CommunityService,
        {
          provide: 'CommunityRepository',
          useClass: repoImpl,
        },
      ],
      exports: [CommunityService],
    };
  }
}

...CommunityControllerModule 将其与 repo 实现一起导入：

import { DomainModule } from 'libs/domain/src';
import { Module } from '@nestjs/common';
import { CommunityController } from './community.controller';
import { CommunityRepositoryImpl } from './community.repository';

@Module({
  imports: [
    DomainModule.register(CommunityRepositoryImpl),
    CommunityRepositoryImpl,
  ],
  controllers: [CommunityController],
  exports: [CommunityRepositoryImpl],
  providers: [
    {
      provide: 'CommunityRepository',
      useClass: CommunityRepositoryImpl,
    },
  ],
})
export class CommunityControllerModule {}

【讨论】：