NestJS中@InjectModel无法解析UserModel依赖问题求助

问题场景 #

在UserRepository中通过@InjectModel()注入UserModel时出现依赖无法解析的错误，已通过独立的MongoProviderModule初始化数据库并导入到UserModule中，尝试显式导出Mongo提供者后问题仍未解决。

相关代码 #

MongoDB提供者模块 #

@Module({
  imports: [
    MongooseModule.forRootAsync({
      imports: [MongoConfigModule],
      useFactory: async (mongoConfigService: MongoConfigService) => ({
        uri: mongoConfigService.dbUrl,
        useNewUrlParser: true,
        isGlobal: true,
      }),
      connectionName: 'user',
      inject: [MongoConfigService],
    }),
  ],
})
export class MongoProviderModule {}

User Schema #

import { Document } from 'mongoose';
import { Schema, Prop, SchemaFactory } from '@nestjs/mongoose';

export type UserDocument = User & Document;

@Schema()
export class User {
  @Prop()
  userId: string;

  @Prop()
  email: string;
}

export const UserSchema = SchemaFactory.createForClass(User);

User Repository（原错误代码） #

import { Injectable } from '@nestjs/common';
import { InjectModel, Model } from '@nestjs/mongoose';
import { FilterQuery } from 'mongoose';
import { User, UserDocument } from './user.schema';

@Injectable()
export class UserRepository {
  constructor(@InjectModel(User.name) private userModel: Model<UserDocument>) {}

  async findOne(userFilterQuery: FilterQuery<User>): Promise<User> {
    return this.userModel.findOne(userFilterQuery);
  }
}

User模块 #

@Module({
  imports: [
    MongoProviderModule,
    MongooseModule.forFeature(
      [{ name: User.name, schema: UserSchema }],
      'user',
    ),
  ],
  controllers: [UserController],
  providers: [UserService, UserRepository],
})
export class UserModule {}

App模块 #

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

错误信息 #

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

Potential solutions:
- If UserModel is a provider, is it part of the current UserModule?
- If UserModel is exported from a separate @Module, is that module imported within UserModule?

问题原因 #

使用了命名数据库连接（connectionName: 'user'），但@InjectModel注入时未指定对应的连接名称，导致Nest无法匹配到正确的Model实例。

解决步骤 #

修改UserRepository中的@InjectModel装饰器，在第二个参数中指定连接名：

@Injectable()
export class UserRepository {
  // 添加连接名参数 'user'
  constructor(@InjectModel(User.name, 'user') private userModel: Model<UserDocument>) {}

  async findOne(userFilterQuery: FilterQuery<User>): Promise<User> {
    return this.userModel.findOne(userFilterQuery);
  }
}

验证要点 #

1. 确保MongooseModule.forRootAsync（MongoProviderModule中）的connectionName与MongooseModule.forFeature（UserModule中）的第二个参数一致
2. @InjectModel的第二个参数必须和上述连接名完全匹配

内容的提问来源于stack exchange，提问作者tnaluat