Nest 无法解析 WithdrawService 的依赖关系答案

【问题标题】：Nest can't resolve dependencies of the WithdrawServiceNest 无法解析 WithdrawService 的依赖关系
【发布时间】：2021-04-28 00:52:04
【问题描述】：

应用程序的架构非常简单，主应用程序有两个控制器。

应用（主要服务）
存款（控制器 + 服务）
撤销（控制器+服务）

在某些情况下，存款服务必须运行提款服务的功能，因此它会初始化提款服务。在我添加 MongoDB 部分之前，一切都非常顺利。

当我将构造函数添加到提取服务时它开始失败：

@Injectable()
export class WithdrawService {
    constructor(@InjectModel('withdraw') private withdrawModel: Model<WithdrawDocument>){}

Withdraw.module.ts：

import { Module } from '@nestjs/common';
import { WithdrawController } from './withdraw.controller';
import { WithdrawService } from './withdraw.service';
import { MongooseModule } from '@nestjs/mongoose';
import { WithdrawSchema } from './dto/withdraw.dto';


@Module({
  imports: [MongooseModule.forFeature([{ name: 'withdraws', schema: WithdrawSchema }])],
  controllers: [WithdrawController],
  providers: [WithdrawService, ],
  exports: [WithdrawService]
})
export class WithdrawModule {}

deposits.module.ts：

import { Module } from '@nestjs/common';
import { DepositsController } from './deposits.controller';
import { DepositsService } from './deposits.service';
import { UtilsModule } from '../utils/utils.module';
import { WithdrawModule } from '../withdraw/withdraw.module';
import { DepositSchema } from './dto/deposit-dto';
import { MongooseModule } from '@nestjs/mongoose';
import { WithdrawSchema } from '../withdraw/dto/withdraw.dto';

@Module({
  imports: [UtilsModule, WithdrawModule, MongooseModule.forFeature([{ name: 'deposits', schema: DepositSchema }])],
  controllers: [DepositsController],
  providers: [DepositsService]
})
export class DepositsModule {}

deposit.service.ts：

@Injectable()
export class DepositsService {

    constructor(private withdrawService: WithdrawService,

...

问题是当 DepositsService 试图初始化 WithdrawService 时，有什么线索可以解决吗？

错误：

Nest can't resolve dependencies of the WithdrawService (?). Please make sure that the argument withdrawModel at index [0] is available in the WithdrawModule context.

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

在将构造函数添加到 WithdrawService 和 mongoDB 部分之前，这两个服务可以通信

【问题讨论】：

标签： node.js mongodb typescript mongoose nestjs

【解决方案1】：

在您的WithdrawModule 中，您使用的是MongooseModule.forFeature([{ name: 'withdraws', schema: WithdrawShcema }])，但在您的WithdrawService 中，您使用的是@InjectModel('withdraw')。在后台，forFeature 创建注入令牌withdrawsModel，@InjectModel() 将注入令牌的元数据设置为withdrawModel。这些令牌不匹配，因此 Nest 无法确定注入什么。您要么需要将MongooseModule 更改为使用withdraw（单数），要么需要将@InjectModel() 更改为使用withdraws（复数）

【讨论】：