Message patterns (request-response) in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a message pattern handler for 'get_data'.

NestJS

import { Controller } from '@nestjs/common';
import { MessagePattern } from '@nestjs/microservices';

@Controller()
export class DataController {
  @MessagePattern('[1]')
  getData() {
    return { data: 'Hello' };
  }
}

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

A'get_data'

B'fetch_data'

C'send_data'

D'update_data'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong or unrelated message pattern string.

Forgetting to put the pattern string inside quotes.

The @MessagePattern decorator listens for the exact message pattern string. Here, 'get_data' is the correct pattern to handle.

2fill in blank

medium

Complete the code to inject the ClientProxy and send a request with 'get_data' pattern.

NestJS

import { Controller, Inject } from '@nestjs/common';
import { ClientProxy } from '@nestjs/microservices';

@Controller()
export class AppController {
  constructor(@Inject('[1]') private client: ClientProxy) {}

  async requestData() {
    return this.client.send('get_data', {}).toPromise();
  }
}

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

A'DATA_SERVICE'

B'MY_SERVICE'

C'CLIENT_PROXY'

D'SERVICE_CLIENT'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a token that was not registered in the module providers.

Forgetting to put the token string inside quotes.

The injection token must match the provider name registered in the module. 'DATA_SERVICE' is the correct token here.

3fill in blank

hard

Fix the error in the message handler to correctly receive data and return a response.

NestJS

import { Controller } from '@nestjs/common';
import { MessagePattern } from '@nestjs/microservices';

@Controller()
export class CalcController {
  @MessagePattern('sum')
  calculate([1]: number[]) {
    return data.reduce((a, b) => a + b, 0);
  }
}

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

Apayload

Bdata

Cnumbers

Dvalues

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name different from the variable used inside the method.

Forgetting to destructure or type the parameter correctly.

The parameter name must match the variable used inside the method. Here, 'data' is used in the reduce function, so it must be the parameter name.

4fill in blank

hard

Fill both blanks to create a message pattern handler that returns the square of a number.

NestJS

import { Controller } from '@nestjs/common';
import { MessagePattern } from '@nestjs/microservices';

@Controller()
export class MathController {
  @MessagePattern([1])
  square([2]: number) {
    return num * num;
  }
}

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

A'square_number'

Bnum

Cvalue

D'calculate_square'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a pattern string that does not match the event.

Using a parameter name different from the variable used inside the method.

The message pattern string should be 'square_number' to match the event. The parameter name 'num' matches the variable used inside the method.

5fill in blank

hard

Fill all three blanks to send a request and handle the response with async/await.

NestJS

import { Controller, Inject } from '@nestjs/common';
import { ClientProxy } from '@nestjs/microservices';

@Controller()
export class AppController {
  constructor(@Inject([1]) private client: ClientProxy) {}

  async getResult() {
    const response = await this.client.send([2], [3]).toPromise();
    return response;
  }
}

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

A'DATA_SERVICE'

B'get_data'

C{}

D'MY_SERVICE'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong injection token.

Sending a wrong or missing message pattern.

Forgetting to provide a payload object.

The injection token is 'DATA_SERVICE' to match the provider. The message pattern is 'get_data' to request data. The payload is an empty object {} as no data is sent.