forgeplus/app/models/wallet.rb

# == Schema Information
#
# Table name: wallets
#
#  id         :integer          not null, primary key
#  balance    :integer
#  user_id    :integer
#  created_at :datetime         not null
#  updated_at :datetime         not null
#

class Wallet < ApplicationRecord
  belongs_to :user
  has_many :outcome, class_name: 'CoinChange', foreign_key: 'from_wallet_id', dependent: :destroy
  has_many :income, class_name: 'CoinChange', foreign_key: 'to_wallet_id', dependent: :destroy
  validates :balance, presence: true
  @@wallet_lock = Mutex.new

  def receive(amount)
    with_lock do
      self.balance += amount
      save!
    end
  end

  def pay(amount)
    with_lock do
      if self.balance < amount
        reload
        return false
      else
        self.balance -= amount
        save!
      end
    end
    true
  end

  def self.wallet_lock
    @@wallet_lock
  end
end