Combining multiple guards in NestJS

Introduction

Guards help protect parts of your app by checking if a user can access them. Combining multiple guards lets you add more than one check easily.

When you want to check if a user is logged in <strong>and</strong> has a specific role before accessing a page.

When you need to verify a user's token <strong>and</strong> confirm their account is active.

When you want to apply different security checks together, like rate limiting <strong>and</strong> permission checks.

When you want to reuse small guard checks and combine them for bigger rules.

Syntax

NestJS

import { UseGuards } from '@nestjs/common';

@UseGuards(FirstGuard, SecondGuard)
export class SomeController {
  // your routes here
}

You list multiple guards inside @UseGuards() separated by commas.

All guards must return true for access to be allowed.

Examples

This example protects the ProfileController with two guards: one for authentication and one for roles.

NestJS

import { UseGuards, Controller, Get } from '@nestjs/common';
import { AuthGuard } from './auth.guard';
import { RolesGuard } from './roles.guard';

@Controller('profile')
@UseGuards(AuthGuard, RolesGuard)
export class ProfileController {
  @Get()
  getProfile() {
    return 'User profile data';
  }
}

Here, two guards protect only the getDashboard route, checking JWT and if the user is active.

NestJS

import { UseGuards, Get, Controller } from '@nestjs/common';
import { JwtGuard } from './jwt.guard';
import { ActiveUserGuard } from './active-user.guard';

@Controller('dashboard')
export class DashboardController {
  @Get()
  @UseGuards(JwtGuard, ActiveUserGuard)
  getDashboard() {
    return 'Dashboard content';
  }
}

Sample Program

This example shows a controller protected by two guards. Both must allow access for the route to work.

NestJS

import { Injectable, CanActivate, ExecutionContext, Controller, Get, UseGuards } from '@nestjs/common';

@Injectable()
class AuthGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean {
    // Simulate user is authenticated
    return true;
  }
}

@Injectable()
class RoleGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean {
    // Simulate user has role
    return true;
  }
}

@Controller('secure')
@UseGuards(AuthGuard, RoleGuard)
export class SecureController {
  @Get()
  getSecureData() {
    return 'Access granted to secure data';
  }
}

Important Notes

Guards run in the order you list them inside @UseGuards().

If any guard returns false, access is denied immediately.

You can apply guards at the controller level or on individual routes.

Summary

Use @UseGuards() with multiple guards separated by commas to combine checks.

All guards must approve access for the user to proceed.

Combining guards helps keep your code clean and reusable.

Practice

1.

What happens when you use @UseGuards(AuthGuard, RolesGuard) on a NestJS route handler?

Choose the best description.

easy

A. Only AuthGuard is checked; RolesGuard is ignored.

B. Both AuthGuard and RolesGuard must allow access for the request to proceed.

C. Either AuthGuard or RolesGuard allowing access is enough to proceed.

D. Guards run in parallel but only the first to approve grants access.

Solution

1. Step 1: Understand how multiple guards work in NestJS

   When multiple guards are used with @UseGuards(), NestJS runs them in sequence and requires all to approve access.

2. Step 2: Apply this to the given guards

   Both AuthGuard and RolesGuard must return true for the request to proceed.

3. Final Answer:

   Both AuthGuard and RolesGuard must allow access for the request to proceed. -> Option B

4. Quick Check:

   All guards must approve = A [OK]

Hint: All guards must pass for access, not just one [OK]

Common Mistakes:

• Thinking only one guard needs to pass
• Assuming guards run in parallel and race
• Believing guards are ignored if one fails

2.

Which of the following is the correct syntax to apply two guards AuthGuard and RolesGuard on a controller method?

?

easy

A. @UseGuards(AuthGuard && RolesGuard)
handleRequest() {}

B. @UseGuards(AuthGuard RolesGuard)
handleRequest() {}

C. @UseGuards(AuthGuard || RolesGuard)
handleRequest() {}

D. @UseGuards(AuthGuard, RolesGuard)
handleRequest() {}

Solution

1. Step 1: Recall the correct syntax for multiple guards

   In NestJS, multiple guards are passed as separate arguments to @UseGuards(), separated by commas.

2. Step 2: Check each option

   @UseGuards(AuthGuard, RolesGuard) handleRequest() {} correctly uses comma-separated guards. @UseGuards(AuthGuard RolesGuard) handleRequest() {} misses the comma between guards, causing a syntax error. Using && or || evaluates to only one guard.

3. Final Answer:

   @UseGuards(AuthGuard, RolesGuard) handleRequest() {} -> Option D

4. Quick Check:

   Comma-separated guards = C [OK]

Hint: Use commas to separate guards, avoid logical operators or missing commas in @UseGuards() [OK]

Common Mistakes:

• Omitting comma between guards
• Using && or || inside @UseGuards()
• Forgetting to separate guards by commas

3.

Given the following code snippet, what will be the output when a request is made?

@UseGuards(AuthGuard, RolesGuard)
@Get('profile')
getProfile() {
  return 'User Profile';
}

// AuthGuard returns true
// RolesGuard returns false

medium

A. Throws an UnauthorizedException

B. Returns 'User Profile'

C. Returns null

D. Returns an empty string

Solution

1. Step 1: Understand guard return values effect

   Guards must all return true to allow access. If any guard returns false, NestJS throws an UnauthorizedException by default.

2. Step 2: Apply given guard results

   Here, AuthGuard returns true but RolesGuard returns false, so access is denied and an exception is thrown.

3. Final Answer:

   Throws an UnauthorizedException -> Option A

4. Quick Check:

   Any guard false = UnauthorizedException [OK]

Hint: All guards must return true; one false blocks access [OK]

Common Mistakes:

• Assuming one guard false still allows access
• Expecting null or empty string instead of exception
• Confusing guard return values with response data

4.

Identify the error in this NestJS controller snippet using multiple guards:

@UseGuards(AuthGuard RolesGuard)
@Get('data')
getData() {
  return 'Data';
}

medium

A. The @Get decorator is misplaced

B. Guards must be passed as an array

C. Missing comma between guards in @UseGuards()

D. Guards cannot be combined on the same method

Solution

1. Step 1: Check syntax of @UseGuards()

   The guards inside @UseGuards() must be separated by commas.

2. Step 2: Identify the error in the snippet

   The snippet misses a comma between AuthGuard and RolesGuard, causing a syntax error.

3. Final Answer:

   Missing comma between guards in @UseGuards() -> Option C

4. Quick Check:

   Comma missing between guards = D [OK]

Hint: Check commas between guards inside @UseGuards() [OK]

Common Mistakes:

• Forgetting commas between guards
• Passing guards as an array incorrectly
• Misplacing decorators order

5.

You want to protect a route so that only authenticated users with the role 'admin' can access it. You have AuthGuard and RolesGuard available. How should you combine them in your controller method?

hard

A. @UseGuards(AuthGuard, RolesGuard) // RolesGuard checks for 'admin' role

B. @UseGuards(RolesGuard, AuthGuard) // Order does not matter

C. @UseGuards(AuthGuard || RolesGuard) // Either guard allows access

D. @UseGuards([RolesGuard, AuthGuard]) // Guards passed as array

Solution

1. Step 1: Understand guard order and combination

   Guards are combined by passing them comma-separated in @UseGuards(). Order matters: AuthGuard first authenticates and sets req.user, then RolesGuard checks the role.

2. Step 2: Choose correct syntax and logic

   @UseGuards(AuthGuard, RolesGuard) // RolesGuard checks for 'admin' role uses correct syntax, order, and notes the role check. Reversing to RolesGuard first fails as no user is set, and claims order irrelevant which is misleading. Array with reversed order fails similarly. Logical operators pass only one guard.

3. Final Answer:

   @UseGuards(AuthGuard, RolesGuard) // RolesGuard checks for 'admin' role -> Option A

4. Quick Check:

   Comma-separated guards with role check = B [OK]

Hint: Use comma-separated guards; RolesGuard checks roles [OK]

Common Mistakes:

• Using logical operators inside @UseGuards()
• Passing guards as an array
• Assuming guard order always matters