Question

I have this query :

city.city_combat_units.includes(:combat_unit).where('combat_units.name = ?', 'unit name')

A city_combat_unit is a combat_unit that belongs to a city. A combat_unit has a name attribute. A city_combat_unit has a city_id and a number_of_units attribute:

CombatUnit
  name

City

CityCombatUnit
  city_id
  combat_unit_id
  number_of_units

What i want to do is get all those city combat units for a city that have a specific name. The best i’ve come up with(in a single line) is the above code, but i fear that i am missing on something way simpler. Am i ?

Answer 1

Try setting up a has_many :through relationship

class City < ActiveRecord::Base
  has_many :city_combat_units
  has_many :combat_units, :through => :city_combat_units
end

class CityCombatUnit < ActiveRecord::Base
  belongs_to :city
  belongs_to :combat_unit
end

class CombatUnit < ActiveRecord::Base
  has_many :city_combat_units
  has_many :cities, :through => :city_combat_units
end

Then you should be able to do something like this

city.combat_units.where(:name => 'unit name')