YalcEventService

The YalcEventService is a service class that provides methods to handle event logging and emitting in a NestJS application using various methods including error handling with different HTTP status codes.

Please read the EventModule documentation for more information on the module that can be used to instantiate the service class.

Also, it might be useful to read the Logger and Errors documentation to understand how these 2 components work since they are used in the event-manager library.

Usage

Import the YalcEventService class from its module and inject it into your service or controller through NestJS's dependency injection mechanism.

import { YalcEventService } from '@nestjs-yalc/event-manager';

Constructor

The YalcEventService constructor takes in three parameters:

• loggerService: ImprovedLoggerService - The logger service to handle logging functionalities.
• eventEmitter: EventEmitter2 - Event emitter for emitting events.
• options?: IEventServiceOptions - Optional parameter for providing service options.

Properties

• logger: ImprovedLoggerService - Provides access to the logger service.
• emitter: EventEmitter2 - Provides access to the event emitter.
• emit - Alias for the log method.

Methods

Logging and Event Emitting

• log and logAsync: Used for logging events synchronously and asynchronously respectively.
• error and errorAsync: Used to log errors synchronously and asynchronously respectively.
• warn and warnAsync: Used to log warnings synchronously and asynchronously respectively.
• debug and debugAsync: Used to log debug events synchronously and asynchronously respectively.
• verbose and verboseAsync: Used to log verbose events synchronously and asynchronously respectively.

All the above methods accept the following parameters:

• eventName: Parameters | string - The name of the event to log.
• options?: IEventOptions - Optional parameter to provide event options.

Error Handling Methods

The following methods are used to throw HTTP errors with various status codes, aiding in semantic error handling:

• errorBadRequest: Throws a 400 Bad Request error.
• errorUnauthorized: Throws a 401 Unauthorized error. ... (shortened for brevity)

Helper Methods

• buildOptions: A protected method used internally to merge method options with the constructor options.

Examples

event.log('user_signup', { detail: 'A new user signed up.' });

event.errorNotFound('resource_not_found', {
  detail: 'The requested resource could not be found.',
});

Note

Ensure to catch errors thrown by these methods in a try-catch block in your application to handle them appropriately. The emit method is an alias to the log method and can be used interchangeably.