section-18.md

Section 18: Understanding Event Flow

Table of Contents

• Section 18: Understanding Event Flow
• Table of Contents
  • Orders Service Events
  • Creating the Events
  • Implementing the Publishers
  • Publishing the Order Creation
  • Publishing Order Cancellation
  • Testing Event Publishing

Orders Service Events

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Creating the Events

import { Subjects } from './subjects';
import { OrderStatus } from './types/order-status';

export interface OrderCreatedEvent {
  subject: Subjects.OrderCreated;
  data: {
    id: string;
    status: OrderStatus;
    userId: string;
    expiresAt: string;
    ticket: {
      id: string;
      price: number;
    };
  };
}

import { Subjects } from './subjects';

export interface OrderCancelledEvent {
  subject: Subjects.OrderCancelled;
  data: {
    id: string;
    ticket: {
      id: string;
    };
  };
}

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Implementing the Publishers

import { Publisher, OrderCreatedEvent, Subjects } from '@chticketing/common';

export class OrderCreatedPublisher extends Publisher<OrderCreatedEvent> {
  subject: Subjects.OrderCreated = Subjects.OrderCreated;
}

import { Subjects, Publisher, OrderCancelledEvent } from '@chticketing/common';

export class OrderCancelledPublisher extends Publisher<OrderCancelledEvent> {
  subject: Subjects.OrderCancelled = Subjects.OrderCancelled;
}

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Publishing the Order Creation

  // Publish an event saying that an order was created
  new OrderCreatedPublisher(natsWrapper.client).publish({
    id: order.id,
    status: order.status,
    userId: order.userId,
    expiresAt: order.expiresAt.toISOString(),
    ticket: {
      id: ticket.id,
      price: ticket.price,
    },
  });

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Publishing Order Cancellation

  // publishing an event saying this was cancelled!
  new OrderCancelledPublisher(natsWrapper.client).publish({
    id: order.id,
    ticket: {
      id: order.ticket.id,
    },
  });

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Testing Event Publishing

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