How to model a customer - merchant transactions model conceptually, like in ActiveRecord for instance?

Question

I have a customer model, a merchant model and a transactions model. Customers can make transactions to merchants and merchants can make transactions to customers as well. Eventually, I'd like to query things like:

1. All transactions made by a customer
2. All transactions made by a merchant
3. All of customer X's transactions to merchant Y (and vice versa)
4. Optional: final all transactions with a certain tag first, and then find all associated merchants and customers related to those transactions. This is a nice-to-have feature, but if it's too complicated to explain in an answer then don't worry about it

So conceptually how should I create associations for each of these models? Like Customers has_many :merchants, through: :transactions (and vice versa)? or use polymorphic associations? etc etc.

Thanks a lot for your help!!!

Answer 1

Conceptually, the Transaction model joins Customer and Merchant, so:

class Customer < ActiveRecord::Base
  has_many :transations
  has_many :merchants, through: :transactions
end

class Merchant < ActiveRecord::Base
  has_many :transactions
  has_many :customers, through: :transactions
end

class Transaction < ActiveRecord::Base
  belongs_to :customer
  belongs_to :merchant
end

To find all of a customer's transactions:

customer.transactions

To find all of a merchant's transactions:

merchant.transactions

Find all of Customer #1's transactions for Merchant #25

customer = Customer.find(1)
customer.transactions.where(merchant_id: 25)

Find all of Merchant #1's transactions for Customer #8

merchant = Merchant.find(1)
merchant.transactions.where(customer_id: 8)

Find all Transactions by a tag (assuming tag is a string field):

transactions = Transaction.where(tag: 'best-seller')

Find all Merchants with Transactions tagged with 'best-seller':

merchants = Merchant.includes(:transaction).where(transaction: {tag: 'best-seller'})

Find all Customer with Transations tagged with 'best-seller':

customers = Customer.includes(:transation).where(transaction: {tag: 'best-seller'})