TLDR:

1. Change the inputs to include an index and optional type ie amount => amount(1i)

2. Add a setter method in the model and handle a hash input:

   class Transaction < ApplicationRecord
   	# …
   
   	def amount=(value)
   		if value.is_a? Hash
   			# do stuff with value[1] etc
   		end
   
   		super(value)
   	end
   
   	# …
   end
   

3. Profit