What is the easiest way to duplicate an activerecord record?

I want to make a copy of an ActiveRecord object, changing a single field in the process (in addition to the id). What is the simplest way to accomplish this?

I realize I could create a new record, and then iterate over each of the fields copying the data field-by-field - but I figured there must be an easier way to do this.

Perhaps something like this:

 new_record = Record.copy(:id)

To get a copy, use the dup (or clone for < rails 3.1+) method:

#rails >= 3.1
new_record = old_record.dup

# rails < 3.1
new_record = old_record.clone

Then you can change whichever fields you want.

ActiveRecord overrides the built-in Object#clone to give you a new (not saved to the DB) record with an unassigned ID.
Note that it does not copy associations, so you'll have to do this manually if you need to.

Rails 3.1 clone is a shallow copy, use dup instead...

Depending on your needs and programming style, you can also use a combination of the new method of the class and merge. For lack of a better simple example, suppose you have a task scheduled for a certain date and you want to duplicate it to another date. The actual attributes of the task aren't important, so:

old_task = Task.find(task_id)
new_task = Task.new(old_task.attributes.merge({:scheduled_on => some_new_date}))

will create a new task with :id => nil, :scheduled_on => some_new_date, and all other attributes the same as the original task. Using Task.new, you will have to explicitly call save, so if you want it saved automatically, change Task.new to Task.create.

Peace.