Copying records

When I was setting up Ruby assignment¹ this week, I wanted to copy all of the exercises and specs from last quarter and associate them with the assignment for this quarter.

I came up with a pretty nice solution using .attributes which returns a Hash of the existing attributes for a record that I can pass straight to the .create method.

new_assignment = Assignment.find(...)
old_assignment = Assignment.find(...)
old_assignment.exercises.each do |e|
  copy = e.attributes
  new_e = new_assignment.exercises.create(copy)
end

BUT this .attributes includes the id too, so this doesn’t work yet. You can exclude key/value pairs from a Hash using .except. You can provide multiple keys at the same time as well.

new_assignment = Assignment.find(...)
old_assignment = Assignment.find(...)
old_assignment.exercises.each do |e|
  copy = e.attributes.except("created_at", "updated_at", "id")
  new_e = new_assignment.exercises.create(copy)
end