What is the purpose of config.ru file?

The databases supported by ActiveRecord without any other gem are:

[1,2,3,5,8,13].include? '8'

a = (1..3).reduce(-6){ |i,x| x + i } puts a

What is the difference between Post.find(3) and Post.find_by_id(3) ?

what does method ActiveSupport::Inflector.constantize do?

Using ERB for views, what filename should be given to a partial called 'login'?

Which of the following validations in Rails checks for null fields?

What does the 4xx series of HTTP errors represent?

How can a partial called 'cart' be rendered from a controller called 'ProductsController', assuming the partial is in a directory called 'shared'?

Which is correctly handles the currency field? A) add_column :items, :price, :decimal, :precision => 8, :scale => 2 B) add_money :items, :price, currency: { present: false }