Question

I have a model named UserPrice which has a form where you can create many UserPrice's at once. I have this virtual attribute called :all_dates which is suppose to update another date_select field of my UserPrice model called :purchase_date but since it isn’t doing its job correctly I need a detailed explanation on this method here so I can get it to work:

def save_all_dates_to_user_prices
 if !self.all_dates.nil?
 self.user_prices.each {|up| up.purchase_date = self.all_dates if up.new_record?}
 end
end

I’ll start out:

1. I defined the method save_all_dates_to_user_prices to happen
   before_save in my UserPrice model.

2. if !self.all_dates.nil? means the UserPrice.all_dates attribute is being check if it is blank or not there (nil?).

This is where I get lost; not being sure on this line:

self.user_prices.each {|up| up.purchase_date = self.all_dates if up.new_record?}

• Its wrapping each UserPrice.user_prices? It wouldn’t look like this if I am trying to get an Array of new records right?
• Why use |up|, is that the self.user_prices.each stands for?
• self.user_prices.each = anything wrapped in the {} (hashes)?

Along with answering the questions I have above could someone fill/correct the details for me about this method?

Thanks, I am new to Rails and Ruby trying to learn as I code.

Answer 1

each is a method of the Enumerable class, which both Array and Hash implement. It takes a block as an argument and simply applies it to all the elements of the Enumerable. So the line you’re asking about translates like this:

for each for the user_prices, assign all_dates to purchase_date if it’s a new user_price

The up is just a variable referring to the current Enumerale element.

Here’s a good explanation of closures in ruby.