Gateway decorator in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @WebSocketGateway decorator in NestJS?

The <code>@WebSocketGateway</code> decorator marks a class as a WebSocket gateway, enabling it to handle real-time communication using WebSockets in a NestJS application.

intermediate

How do you specify the WebSocket server options using the @WebSocketGateway decorator?

You pass an options object to the @WebSocketGateway decorator, for example: @WebSocketGateway({ namespace: '/chat', transports: ['websocket'] }) to configure namespace and transport methods.

beginner

Which NestJS module must be imported to use the @WebSocketGateway decorator?

You must import <code>@WebSocketGateway</code> from <code>@nestjs/websockets</code> to use the <code>@WebSocketGateway</code> decorator in your class.

intermediate

Can a class decorated with <code>@WebSocketGateway</code> handle multiple WebSocket events? How?

Yes, by adding methods decorated with @SubscribeMessage('eventName') inside the gateway class, you can handle multiple WebSocket events.

advanced

What is the difference between @Gateway and @WebSocketGateway decorators in NestJS?

In NestJS, @WebSocketGateway is the correct decorator to create a WebSocket gateway. @Gateway is not a standard decorator; the official one is @WebSocketGateway. Sometimes @Gateway is used informally to refer to it.

Which decorator do you use to create a WebSocket gateway in NestJS?

A @WebSocketGateway

B @Gateway

C @SocketServer

D @SubscribeMessage

The correct decorator to create a WebSocket gateway is @WebSocketGateway.

How do you listen to a WebSocket event named 'message' inside a gateway class?

A Use @Listen('message') on a method

B Use @OnEvent('message') on a method

C Use @SubscribeMessage('message') on a method

D Use @WebSocketListener('message') on a method

You use @SubscribeMessage('message') to listen to WebSocket events named 'message'.

Where do you import the @WebSocketGateway decorator from?

A @nestjs/common

B @nestjs/websockets

C socket.io

D @nestjs/core

The @WebSocketGateway decorator is imported from @nestjs/websockets.

Which option can you set in the @WebSocketGateway decorator?

A namespace

B database

C template

D middleware

You can set the 'namespace' option to define the WebSocket namespace.

What does the @SocketServer decorator do inside a gateway class?

A Configures transport options

B Marks a method as an event handler

C Defines the gateway namespace

D Injects the WebSocket server instance

@SocketServer injects the WebSocket server instance to use inside the gateway.

Explain how to create a WebSocket gateway in NestJS and handle a custom event.

Think about the decorator for the class and the decorator for event methods.

Describe how to configure a WebSocket gateway namespace and access the server instance.

Focus on decorator options and property decorators inside the class.