Question

My method loads a list of countries(code, name) into the database, but before that it has to check, if the country data does not already exist. This works fine:

 def self.load_countries
    get_countries.each do |country|
      code, name = country
      if find_by_code(code).nil?
        create({ 'name' => name, 'code' => code })
      end
    end
  end

However, as I am new to Ruby, I want to learn the best practises. So, in this code I am not sure about two things which might be (or might not be) optimised:

1. find_by_attribute returns the “select * from table” statement. In this case, when I don’t need any data from database – I just want to know if the record exists or not – selecting the entire row seems a little inefficient to me. Is there any better way solve this? For example, “select 1 from table where …” using ActiveRecord?

2. This question might be silly, but I want to be sure: when I start the loop with the get_countries.each, is it ok to use a method instead of a variable? Isn’t the same method called each cycle (N times)? In other words, would this be anymore efficient:

   countries = get_countries

   countries.each do |country|

Any comments on those few lines of code are welcome, since the fact it works doesn’t necessarily mean that I am doing it the right way.

Thank you.

Answer 1

You can use the exists? function in ActiveRecord.

def self.load_countries
  get_countries.each do |country|
    code, name = country
    unless exists?(:code => code)
      create({ :name => name, :code => code })
    end
  end
end

The get_countries function gets called only once. It returns an enumerable data type and then the each walks through each of them.