javascript - Nest无法解析自定义服务的依赖关系

Question

我基本上遵循本教程并进行了很小的修改:link

我在节点 12.10.0 上使用 Nest 6.14.2。运行我的应用程序时，我得到:

> recon-backend@0.0.1 start C:\Users\e5553079\Desktop\Node_Projects\recon-backend
> nest start

[Nest] 8324   - 02/10/2020, 9:28:21 AM   [NestFactory] Starting Nest application...
[Nest] 8324   - 02/10/2020, 9:28:21 AM   [InstanceLoader] MongooseModule dependencies initialized +53ms
[Nest] 8324   - 02/10/2020, 9:28:21 AM   [ExceptionHandler] Nest can't resolve dependencies of the ReconQueryService (?). Please make sure that the argument ReconQueryModel at index [0] is available in the AppModule context.

Potential solutions:
- If ReconQueryModel is a provider, is it part of the current AppModule?
- If ReconQueryModel is exported from a separate @Module, is that module imported within AppModule?
  @Module({
    imports: [ /* the Module containing ReconQueryModel */ ]
  })
 +2ms
Error: Nest can't resolve dependencies of the ReconQueryService (?). Please make sure that the argument ReconQueryModel at index [0] is available in the AppModule context.

我的文件如下所示:

<强>1。 app.module.ts

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { MongooseModule } from '@nestjs/mongoose';
import { ReconQueryModule } from './reconQuery/reconQuery.module';
import { ReconQueryService } from './reconQuery/reconQuery.service';
import { ReconQueryController } from './reconQuery/reconQuery.controller';
@Module({
  imports: [
    MongooseModule.forRoot('mongodb://localhost/backend-app', { useNewUrlParser: true }),
    ReconQueryModule
  ],
  controllers: [AppController, ReconQueryController],
  providers: [AppService, ReconQueryService],
})
export class AppModule {}

<强>2。 reconQuery.service.ts

import { Injectable } from '@nestjs/common';
import { Model } from 'mongoose';
import { InjectModel } from '@nestjs/mongoose';
import { ReconQuery } from './interfaces/reconQuery.interface';
import { CreateReconQueryDTO } from './dto/create-reconQuery.dto';

@Injectable()
export class ReconQueryService {
    constructor(@InjectModel('ReconQuery') private readonly reconQueryModel: Model<ReconQuery>) { }
    // Fetch all queries
    async getAllQueries(): Promise<ReconQuery[]> {
        const queries = await this.reconQueryModel.find().exec();
        return queries;
    }
...

<强>3。 reconQuery.interface.ts

import { Document } from 'mongoose';

export interface ReconQuery extends Document {
    readonly id: number;
    readonly name: string;
    readonly sql: string;
}

<强>4。 reconQuery.module.ts

import { Module } from '@nestjs/common';
import { ReconQueryController } from './reconQuery.controller';
import { ReconQueryService } from './reconQuery.service';
import { MongooseModule } from '@nestjs/mongoose';
import { ReconQuerySchema } from './schemas/reconQuery.schema';
@Module({
  imports: [
    MongooseModule.forFeature([{ name: 'ReconQuery', schema: ReconQuerySchema }])
  ],
  controllers: [ReconQueryController],
  providers: [ReconQueryService]
})
export class ReconQueryModule {}

我想知道为什么它会提示 ReconQueryModel 因为我没有这样的实体，只有一个 ReconQuery 接口(interface)。

Answer 1

您还有额外的ReconQueryService提供于AppModule .

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { MongooseModule } from '@nestjs/mongoose';
import { ReconQueryModule } from './reconQuery/reconQuery.module';
import { ReconQueryService } from './reconQuery/reconQuery.service';
import { ReconQueryController } from './reconQuery/reconQuery.controller';
@Module({
  imports: [
    MongooseModule.forRoot('mongodb://localhost/backend-app', { useNewUrlParser: true }),
    ReconQueryModule
  ],
  controllers: [AppController, ReconQueryController],
  providers: [AppService, ReconQueryService], // <-- this causes the error
})
export class AppModule {}

@InjectModel()通过调用MongooseModule.forFeature(...)提供在某个@Module() 。 ReconQueryService在ReconQueryModule很好，因为那就是 MongooseModule.forFeature()如此称呼@InjectModel()已正确提供。然而，在 AppModule ，你没有MongooseModule.forFeature()因此 Nest 无法解析 @InjectModel()对于 ReconQueryService .

检查您是否确实需要使用 ReconQueryService在AppModule (AppModule 中声明的服务和 Controller )。如果不这样做，请删除 ReconQueryService来自providers大批。如果您这样做，请转到ReconQueryModule并执行以下操作:

import { Module } from '@nestjs/common';
import { ReconQueryController } from './reconQuery.controller';
import { ReconQueryService } from './reconQuery.service';
import { MongooseModule } from '@nestjs/mongoose';
import { ReconQuerySchema } from './schemas/reconQuery.schema';
@Module({
  imports: [
    MongooseModule.forFeature([{ name: 'ReconQuery', schema: ReconQuerySchema }])
  ],
  controllers: [ReconQueryController],
  providers: [ReconQueryService],
  exports: [ReconQueryService] // <-- add this line
})
export class ReconQueryModule {}

导出的内容将可以在提供它们的模块之外使用。只需将该模块导入到其他地方即可。