Rails如何按平均价格订购记录

Question

I am trying to set the order of records returned by the controller by price. The problem is that there are 3 different price options and it is possible for just 1 price, 2 prices or all prices to be used on each record. So I have decided to set the position by average price. To get the average price I anticipate taking the sum of available prices and dividing by the available price count.

Currently i'm setting the order by id:

def category
    @manufacturers = Manufacturer.order("manufacturers.id ASC").where(:visible => true)
end

Each record has :hp_price, :ch_price, :mp_price (all monthly payment prices) so I imagine I want to check if each option is set and, if so, add it to an array which I can later run the calculation on (maybe this isn't the best way?).

I am a bit stumped as to how to go about doing this (I'm new to rails). Could I do this in-line in the controller? (if so should i even do this?)

something to the effect of:

def category
    @manufacturers = Manufacturer.order((manufacturers.hp_price+manufacturers.ch_price+manufacturers.mp_price)/3 ASC).where(:visible => true)
end

Or another possibility would be to add an average price column to each record and just work it out when the record is created (it feels like that is a bit of an over-the-top solution to me though).

I guess i'd like to know what you would consider best practice in such a situation as, like i said, I am new to this and i'm worried that the solution that I would come up with if I just muddle on through would be a bit hacky!

Answer 1

Refer the columns like this and it should work

def category
  @manufacturers = Manufacturer.order("(hp_price+ch_price+mp_price)/3 asc").where(:visible => true)
end