find_by_sql in Rails, accessing the resulting array

Question

I\'m trying to run a query in a very quick and dirty way in Rails, without putting the rest of the model in place. I know this is bad practice but I just need a quick resul

Answer 1

Since you are defining an instance method, I think it should return the price if it exists or nil

Try something like this:

def shipping_price
  ShippingZonePrice.find_by_sql(
    "SELECT z.price as price
     FROM shipping_zone_prices z, items i
     WHERE i.id = '#{self.id}'
     AND z.weight_g > d.weight
     ORDER BY z.weight_g asc limit 1").first.try(:price)
end

Then this should work for you:

@item.shipping_price

The first.try(:price) part is needed because find_by_sql may return an empty array. If you tried to do something like first.price on an empty array, you would get an exception along the lines of NoMethodError: undefined method 'price' for nil:NilClass.