Ruby on Rails QuickTip: Adding Parameters to your Methods Safely

This is going to be a quick post and applies to a lot of different languages, but it's something we've been doing in our Rails projects a decent amount.

If you're ever working on a larger codebase and you decide you want to add a parameter to a method, but are afraid to do so because it might break code elsewhere, consider simply adding a default value.

Take the following setup for example

class MyModel < ApplicationRecord
  def my_method(user_id)
    user = User.find user_id
    user
  end
end

Now, let's say you want to modify this method so you can add another parameter. Here's a safe way you can do it:

class MyModel < ApplicationRecord
  def my_method(user_id, new_parameter=nil)
    user = User.find user_id
    if new_parameter
      do something
    end
    user
  end
end

Now that new parameter's default value could have been anything, but the key here:

1. Have a default value so that any code calling this method with the original parameters will still work
2. When the new parameter is not passed in, have the method behave the exact same way it did before

With these two principles you'll be able to extend your code without breaking any existing code.