CODESAMPLE

Publish-Subscribe - Ruby

Publish-Subscribe Ruby

The Publish-Subscribe (Pub/Sub) pattern decouples message senders (publishers) from message receivers (subscribers). Publishers don’t know who is receiving messages, and subscribers don’t need to know where messages come from. A central message broker (in this case, a simple Ruby hash) manages subscriptions.

This Ruby implementation uses a hash to store subscribers for each topic. Publishers call publish with a topic and message, iterating through subscribers to notify them. Subscribers register with subscribe providing a topic and a callback. The use of blocks for callbacks is idiomatic Ruby, enabling concise and flexible event handling. The topics hash acts as the central registry, and the structure promotes code readability and ease of maintenance.

class Event
  attr_reader :topic, :data

  def initialize(topic, data)
    @topic = topic
    @data = data
  end
end

class PubSub
  def initialize
    @topics = {}
  end

  def subscribe(topic, &callback)
    @topics[topic] ||= []
    @topics[topic] << callback
  end

  def publish(topic, data)
    @topics[topic].each do |callback|
      callback.call(Event.new(topic, data))
    end
  end
end

# Example Usage:

pub_sub = PubSub.new

pub_sub.subscribe("user.created") do |event|
  puts "User created! Topic: #{event.topic}, Data: #{event.data}"
end

pub_sub.subscribe("user.created") do |event|
  puts "Sending welcome email to: #{event.data[:email]}"
end

pub_sub.subscribe("order.placed") do |event|
  puts "New Order! Order ID: #{event.data[:order_id]}"
end

pub_sub.publish("user.created", { username: "john_doe", email: "john.doe@example.com" })
pub_sub.publish("order.placed", { order_id: "12345", total: 100.00 })