Nest 无法解析 JwtService 的依赖关系答案

【问题标题】：Nest can't resolve dependencies of the JwtServiceNest 无法解析 JwtService 的依赖关系
【发布时间】：2021-11-17 18:51:25
【问题描述】：

我在这里创建了一些模块，但我遇到了一个错误

认证模块

   import { Module } from "@nestjs/common";
import { AuthService } from "./auth.service";
import { LocalStrategy } from "./local.strategy";
import { JwtStrategy } from "./jwt.strategy";
import { UsersModule } from "../users/users.module";
import { PassportModule } from "@nestjs/passport";
import { JwtModule, JwtService } from "@nestjs/jwt";
import { jwtConstants } from "./constants";
import { ConfigModule, ConfigService } from "@nestjs/config";

@Module({
    imports: [
        UsersModule,
        PassportModule,
        JwtModule.register({
            secret: jwtConstants.secret,
            signOptions: { expiresIn: "1d" },
        }),
    ],
    providers: [AuthService, LocalStrategy, JwtStrategy],
    exports: [AuthService, LocalStrategy, JwtStrategy],
})
export class AuthModule {}

电子邮件模块

  import { Module } from "@nestjs/common";
import EmailService from "./email.service";

import { ConfigModule } from "@nestjs/config";

import { EmailConfirmationService } from "./emailConfirmation.service";
import { EmailConfirmationController } from "./emailConfirmation.controller";
import { EmailConfirmationGuard } from "./guards/emailConfirmation.guard";
import { AuthModule } from "src/auth/auth.module";
import { UsersModule } from "src/users/users.module";

@Module({
    imports: [ConfigModule,AuthModule,UsersModule],
    providers: [EmailService,EmailConfirmationService,EmailConfirmationGuard],
    exports: [EmailConfirmationService,EmailConfirmationGuard],
    controllers : [EmailConfirmationController]
})
export class EmailModule {}

用户模块

import { Module } from "@nestjs/common";
import { UsersService } from "./users.service";
import { UsersController } from "./users.controller";
import { MongooseModule } from "@nestjs/mongoose";
import { UserSchema } from "./entities/user.entity";
import { EmailModule } from "src/email/email.module";

@Module({
    imports: [MongooseModule.forFeature([{ name: "User", schema: UserSchema }]),EmailModule],
    providers: [UsersService],
    exports: [UsersService],
    controllers: [UsersController],
})
export class UsersModule {}

我面临的错误

 [Nest] 9200  - 09/26/2021, 3:43:15 PM   ERROR [ExceptionHandler] Nest cannot create the EmailModule instance.
The module at index [1] of the EmailModule "imports" array is undefined.

Potential causes:
- A circular dependency between modules. Use forwardRef() to avoid it. Read more: https://docs.nestjs.com/fundamentals/circular-dependency
- The module at index [1] is of type "undefined". Check your import statements and the type of the module.

Scope [AppModule -> AuthModule -> UsersModule]
Error: Nest cannot create the EmailModule instance.
The module at index [1] of the EmailModule "imports" array is undefined.

Potential causes:
- A circular dependency between modules. Use forwardRef() to avoid it. Read more: https://docs.nestjs.com/fundamentals/circular-dependency
- The module at index [1] is of type "undefined". Check your import statements and the type of the module.

我错过了什么？

EmailConfirmationService is used in UsersController
UserService is used in EmailConfirmationService

【问题讨论】：

标签： javascript jwt nestjs

【解决方案1】：

为了在您的 UserController 中使用 EmailService，并且在 EmailConfirmationService 中使用 UserService，您必须在 UserModule 中执行类似的操作：

imports: [forwardRef(() => EmailModule)]

在 EmailModule 内部为 UserModule 做同样的事情：

imports: [forwardRef(() => UserModule)]

其余的导入应该没有 forwardRef(()=>)

你可以在这里阅读更多关于循环依赖的信息https://docs.nestjs.com/fundamentals/circular-dependency

【讨论】：

【解决方案2】：

您的导入中列出了JwtService。导入仅适用于模块。

也分享来自JwtService的代码，以便我们确保没有其他问题。

更新：如果EmailModule 想要使用来自AuthModule 的导出（在本例中为JwtService），则必须将AuthModule 添加到其导入数组中。

这是 DI 系统的全部前提，模块之间通过将它们打算共享的东西放在exports 数组中来共享东西。之后，任何模块都可以将 Source 模块添加到其imports 数组中，以访问源导出的内容。错误消息为您逐字逐句说明：

If JwtService is exported from a separate @Module, is that module imported within EmailModule? @Module({ imports: [ /* the Module containing JwtService */ ] })

【讨论】：