find_each活动记录查询

Question

I have this method in my model to allow my view to display all equipment associated with a vehicle. Should I be using find_each to check batches of records, and if so, how would I break this method down to use it?

def equip(vehicle)
  equip = Vehicle.find_by_id(vehicle).equipments.
        where("vehicle_id = ?", vehicle).all
end

Answer 1

Don't use .all at the end, it will trigger the query when its called and will be a pain as perfomances.

Also, you should use this syntax (Rails 3):

def equip(vehicle)
  equip = Equipment.where(vehicle_id: vehicle.try(:id) || vehicle)
end

Using this, you only use the Equipment model, which will just use the equipments SQL table (not 2 or more).

# This line
vehicle.try(:id) || vehicle
# Allows you to pass both a Vehicle object or a vehicle id to your method

Also, if you have already an instance of vehicle, you could use:

def equip(vehicle)
  equip = Vehicle.where(id: vehicle).first.equipments
  # or with your syntax:
  equip = Vehicle.find(vehicle).equipments
end