Question

Lets say I am wrapping an ActiveRecord class for some reason and I have defined a create class method.

class BusCreator
  def self.create(attr)
    bus = Bus.new(attr)
    bus.departure_time = bus.arrival_time - bus.trip_duration
    bus.save
    bus
  end
end

What’s the best way to also define a create! method on BusCreator? Obviously, it should execute the same logic as BusCreator.create but should call save! instead of save.

Answer 1

The best answer depends to some extent on what you want create! to do. If you want it to do the same thing as create, but raise an exception on failure, you could do something like this:

class BusCreator
  def self.create(attr)
    bus = build_bus(attr)
    bus.save
    bus
  end

  def self.create!(attr)
    bus = create(attr)
    if bus.new_record? # check if save succeeded
      raise MyException, 'creation failed!'
    end
    bus
  end
end

class MyException < StandardError; end

Otherwise this is simply a matter of extracting the common elements of the methods into a different method which acts as a helper:

class BusCreator
  def self.create(attr)
    bus = build_bus(attr)
    bus.save
    bus
  end

  def self.create!(attr)
    bus = build_bus(attr)
    bus.save!
    bus
  end

  private  

  def self.build_bus(attr)
    bus = Bus.new(attr)
    bus.departure_time = bus.arrival_time - bus.trip_duration
  end
end

There are lots of style options here, if you really wanted to minimize duplication you could do something like this:

class BusCreator
  def self.create(attr)
    bus = build_bus(attr)
  end

  def self.create!(attr)
    bus = build_bus(attr, true)
  end

private  

  def self.build_bus(attr, big_save=false)
    bus = Bus.new(attr)
    bus.departure_time = bus.arrival_time - bus.trip_duration
    big_save ? bus.save! : bus.save
    bus
  end
end