CRUD operations in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the necessary decorator for creating a controller in NestJS.

NestJS

import { [1] } from '@nestjs/common';

@Controller('items')
export class ItemsController {}

Drag options to blanks, or click blank then click option'

AController

BInjectable

CModule

DGet

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Injectable instead of @Controller

Importing a decorator not related to controllers

The @Controller decorator is used to define a controller in NestJS.

2fill in blank

medium

Complete the code to define a GET route handler method named 'findAll' in the controller.

NestJS

@Controller('items')
export class ItemsController {
  @[1]()
  findAll() {
    return 'This action returns all items';
  }
}

Drag options to blanks, or click blank then click option'

APost

BDelete

CPut

DGet

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Post instead of @Get

Forgetting the parentheses after the decorator

The @Get() decorator defines a handler for HTTP GET requests.

3fill in blank

hard

Fix the error in the method to accept an 'id' parameter from the URL path.

NestJS

@Get(':id')
findOne(@[1]('id') id: string) {
  return `This action returns item #${id}`;
}

Drag options to blanks, or click blank then click option'

ABody

BParam

CQuery

DHeaders

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Body instead of @Param

Using @Query for path parameters

The @Param('id') decorator extracts the 'id' parameter from the URL path.

4fill in blank

hard

Fill both blanks to create a POST method that accepts a data object from the request body and returns it.

NestJS

@Post()
create(@[1]() createItemDto: any) {
  return [2];
}

Drag options to blanks, or click blank then click option'

ABody

BcreateItemDto

CRequest

DResponse

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Request instead of @Body

Returning the wrong variable

The @Body() decorator extracts the request body, and returning createItemDto sends back the received data.

5fill in blank

hard

Fill all three blanks to create a DELETE method that accepts an 'id' parameter and returns a confirmation string.

NestJS

@Delete(':id')
remove(@[1]('id') id: string) {
  return `Item with id ${id} has been [2]`;
}

// Use this method in the controller to handle deletion requests.

Drag options to blanks, or click blank then click option'

AParam

Bdeleted

Cremoved

DBody

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Body instead of @Param

Using 'deleted' instead of 'removed' in the message

The @Param('id') decorator extracts the 'id' from the URL, and the string uses 'removed' to confirm deletion.

Practice

1. In NestJS, which decorator is used in a controller method to handle HTTP POST requests for creating data?

easy

A. @Post

B. @Get

C. @Put

D. @Delete

Solution

1. Step 1: Understand HTTP methods and their NestJS decorators

   HTTP POST is used to create new data. NestJS uses @Post decorator for this.

2. Step 2: Match the decorator to the HTTP method

   @Get is for reading, @Put for updating, and @Delete for deleting data, so they don't fit creating data.

3. Final Answer:

   @Post -> Option A

4. Quick Check:

   POST = @Post [OK]

Hint: POST requests use @Post decorator in NestJS controllers [OK]

Common Mistakes:

• Confusing @Get with @Post
• Using @Put for creating data
• Using @Delete for creation

2. Which of the following is the correct way to extract a route parameter named id in a NestJS controller method?

easy

A. async getItem(@Body('id') id: string) {}

B. async getItem(@Query('id') id: string) {}

C. async getItem(@Param('id') id: string) {}

D. async getItem(@Headers('id') id: string) {}

Solution

1. Step 1: Identify the decorator for route parameters

   @Param is used to extract parameters from the URL path, such as /items/:id.

2. Step 2: Check other decorators and their uses

   @Body extracts data from the request body, @Query from query strings, and @Headers from HTTP headers, so they don't get route params.

3. Final Answer:

   async getItem(@Param('id') id: string) {} -> Option C

4. Quick Check:

   Route param = @Param [OK]

Hint: Use @Param to get URL parameters in NestJS [OK]

Common Mistakes:

• Using @Body to get URL params
• Using @Query for route params
• Confusing @Headers with @Param

3. Given this NestJS controller method, what will be the response if a client sends a DELETE request to /items/5 and the service deletes the item successfully?

  @Delete(':id')
  async remove(@Param('id') id: string) {
    await this.itemsService.delete(id);
    return { message: `Item ${id} deleted` };
  }

medium

A. HTTP 404 Not Found

B. { "message": "Item 5 deleted" }

C. { "error": "Item not found" }

D. Empty response with HTTP 204 No Content

Solution

1. Step 1: Analyze the controller method's return value

   The method returns an object with a message string including the id parameter.

2. Step 2: Understand the response for successful deletion

   Since the method returns a JSON object with the message, the client receives that JSON with HTTP 200 OK by default.

3. Final Answer:

   { "message": "Item 5 deleted" } -> Option B

4. Quick Check:

   Return JSON message on success = { "message": "Item 5 deleted" } [OK]

Hint: Returned object becomes JSON response by default in NestJS [OK]

Common Mistakes:

• Expecting HTTP 204 No Content without explicit status
• Assuming error response without checking service
• Confusing DELETE with GET response

4. Identify the error in this NestJS controller method for updating an item:

  @Put(':id')
  async update(@Body() updateDto: UpdateItemDto) {
    return this.itemsService.update(updateDto.id, updateDto);
  }

medium

A. Method should be named create, not update

B. Using @Body instead of @Query for update data

C. UpdateItemDto cannot be used in @Body

D. Missing @Param decorator to get the id from URL

Solution

1. Step 1: Check how the id is obtained

   The method expects id from updateDto.id, but the route has ':id' parameter which is not extracted.

2. Step 2: Identify missing @Param decorator

   To get id from URL, @Param('id') id: string should be added as a parameter to the method.

3. Final Answer:

   Missing @Param decorator to get the id from URL -> Option D

4. Quick Check:

   URL param needs @Param [OK]

Hint: Use @Param to get URL id in update methods [OK]

Common Mistakes:

• Assuming id comes from body without @Param
• Confusing @Body with @Query
• Ignoring route parameters

5. You want to implement a NestJS controller method to update an item by its id from the URL and new data from the request body. Which of the following method signatures correctly follows NestJS CRUD patterns?

hard

A. async update(@Param('id') id: string, @Body() updateDto: UpdateItemDto) { return this.itemsService.update(id, updateDto); }

B. async update(@Body('id') id: string, @Body() updateDto: UpdateItemDto) { return this.itemsService.update(id, updateDto); }

C. async update(@Query('id') id: string, @Body() updateDto: UpdateItemDto) { return this.itemsService.update(id, updateDto); }

D. async update(@Param() params: any) { return this.itemsService.update(params.id, params); }

Solution

1. Step 1: Identify correct decorators for id and body

   Use @Param('id') to get id from URL and @Body() to get update data object.

2. Step 2: Check method parameters and service call

   async update(@Param('id') id: string, @Body() updateDto: UpdateItemDto) { return this.itemsService.update(id, updateDto); } correctly separates id and updateDto and calls service with both.

3. Final Answer:

   async update(@Param('id') id: string, @Body() updateDto: UpdateItemDto) { return this.itemsService.update(id, updateDto); } -> Option A

4. Quick Check:

   Use @Param for id, @Body for data [OK]

Hint: Use @Param('id') and @Body() together for update methods [OK]

Common Mistakes:

• Using @Body('id') instead of @Param('id')
• Using @Query for route params
• Passing params object instead of separate arguments