Question

I am new to rails and getting stuck a lot trying to develop my first app. I have a rails 3.2.2 application with the following tables (simplified):

Vehicle (has_many :checklists)
number:string
license_plate:string

Checklist (belongs_to :vehicle)
vehicle_id:integer
mileage:integer

I need to display a table listing every vehicle and mileage difference between two given dates like the following:

From: 2012/05/01
To:2012/06/01
Vehicle number    License plate    Mileage difference
000001            LIH576           453
000002            KUL763           158
000003            OSF473           631

I couldn’t figure out how to come up with the Mileage difference value. Any help would be greatly appreciated.

Thanks!
Corix

Answer 1

Well, you could subtract the mileage of from and to dates.

c1 = Checklist.where(:vehicle_id => 1, :check_date => FROM_DATE)
c2 = Checklist.where(:vehicle_id => 1, :check_date => TO_DATE)

difference = c2.mileage - c1.mileage

Assuming the to date is the most recent.