Building a Reward System with Rails

After implementing our basic referral system using the Refer gem, we needed to build a flexible reward system on top of it. This system needed to handle various reward scenarios: when users refer others, when referred users complete trial bookings, and when they subscribe to our service. Here's how we approached this challenge in our Rails monolith application.

Understanding the Components

Before diving into the implementation, let's understand the key components:

• Trigger: The specific event that causes a reward to be created (e.g., completing a trial booking)

• Source: The original cause that led to the reward (typically the referral)

• Recipient: The user or household that receives the reward

• Amount: The reward value, stored in cents for precision using the money-rails gem

The Core: The Reward Model

At the heart of our system is the Reward model:

class Reward < ApplicationRecord
  belongs_to :recipient, polymorphic: true
  belongs_to :trigger, polymorphic: true, optional: true
  belongs_to :source, polymorphic: true, optional: true

  monetize :amount_cents

  enum reason: {
    trial_start: 'trial_start',
    sub_complete: 'sub_complete',
    signup_discount: 'signup_discount'
  }, _prefix: true

  scope :unredeemed, -> { where(redeemed_at: nil) }

  # ... methods for creating specific rewards ...
end

The Rewardable Concern

To make it easy to add reward functionality to different models, we created a Rewardable concern:

# app/models/concerns/rewardable.rb

module Rewardable
  extend ActiveSupport::Concern

  included do
    has_many :rewards, as: :recipient
  end

  def total_earned
    Money.new(rewards.sum(:amount_cents), "CAD")
  end

  def unredeemed_rewards
    rewards.unredeemed
  end

  def redeem_rewards!
    unredeemed_rewards.update_all(redeemed_at: Time.current)
  end
end

Extending the Referral Model

We extended the Refer gem's Referral model to integrate with our reward system:

module ReferralExtensions
  extend ActiveSupport::Concern

  included do
    has_many :rewards, as: :source
  end

  def create_trial_rewards(trial_booking)
    Reward.create_for_trial_start(self, trial_booking)
  end

  def complete_subscription(subscription)
    Reward.create_for_sub_complete(self, subscription)
  end
end

# In config/initializers/refer.rb
Rails.application.config.to_prepare do
  Refer::Referral.include ReferralExtensions
end

Triggering Rewards

We set up our Booking model to trigger rewards when a booking is completed, as an example:

class Booking < ApplicationRecord
  after_save :create_trial_start_reward, if: :status_changed_to_completed?

  private

  def create_trial_start_reward
    referral = Refer::Referral.find_by(referred: household.owner)
    Reward.create_for_trial_start(referral, self) if referral
  end

  def status_changed_to_completed?
    saved_change_to_status? && completed?
  end
end

Conclusion

This flexible reward system allows us to easily add new types of rewards and associate them with different actions in our application. The use of polymorphic associations provides the flexibility to link rewards to various models, while the money-rails gem ensures precise handling of monetary amounts. The system has proven to be robust and easily extendable as our referral program grows.

The combination of the Refer gem for handling referrals and our custom reward system has created a powerful tool for incentivizing user growth and engagement on our platform.