Open-source, Ruby, Software

Attack of the Clones

This is an elementary Rails tip, but one that I just recently stumbled into. When working in a project where you have a record that you want to make multiple instances of, you can do it the old fashioned way:

User.create(:first_name => 'Laurence;', :last_name => 'Tureaud', :alias => 'Mr. T')

However, this is quite a bit of typing. If you want multiple users, you can add a loop structure like this:

(1..5).each {User.create(:first_name => 'Laurence;', :last_name => 'Tureaud', :alias => 'Mr. T')}

This will create 5 Mr. T’s! Of course, if you have any validations checking for unique values, this might fail. I would recommend using the loop structure to prefix, or postfix a unique digit:

(1..5).each {|x| User.create(:first_name => 'Laurence;', :last_name => "Tureaud#{x}", :alias => 'Mr. T')}

Notice that the “x” will be a different value in each loop. Now for the grand finale, you can save all this typing and use a method on an ActiveRecord object called “clone”. From the official Rails docs:

Returns a clone of the record that hasn‘t been assigned an id yet and is treated as a new record. Note that this is a “shallow” clone: it copies the object‘s attributes only, not its associations. The extent of a “deep” clone is application-specific and is therefore left to the application to implement according to its need.

To use this, grab the record you want to clone first:

user = User.find(1)
# "Tureaud">

Note that this does not work on a collection of ActiveRecord objects – only an individual object. Now, call the clone method, and this removes the id attribute:

user = User.find(1)
# "Tureaud">
new_user = user.clone
# "Tureaud">

I have now cloned my object. With some method chaining, and some looping, we can easy mass create fake records:

user = User.find(1)
# "Tureaud">
(1..5).each {}

Much less typing! Now, with all that time you saved, go sign up for an Amazon Prime account and buy some cool stuff and get it shipped for free!


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