Service Objects

What are Service Objects

Service objects are Plain Old Ruby Objects (POROs) which encapsulate a whole business process/user interaction.

Our services are located in app/services with the corresponding specs in spec/services. Their main interface is a class level method named call, as in the following example:

class ImportUsers  def self.call(arg1)    new(arg1).call  end
  def initialize(arg1)    @arg1 = arg1  end
  def call    # import code goes here  endend

To distinguish services from models we often give them verb names vs noun names, e.g. ImportUsers instead of UserImporter.

Generating Service Objects

To make our services more consistent we use a custom Rails generator. Some usage examples:

Generate a non-namespaced service without arguments

$ rails generate service DoTheThing

# app/services/do_the_thing.rbclass DoTheThing  def self.call    new.call  end
  def call  endend

# spec/services/do_the_thing_spec.rbrequire "rails_helper"
RSpec.describe DoTheThing, type: :service do  pending "add some examples to (or delete) #{__FILE__}"end

Generate a non-namespaced service with arguments:

$ rails generate service DoTheThing arg1 arg2

# app/services/do_the_thing.rbclass DoTheThing  def self.call(arg1, arg2)    new(arg1, arg2).call  end
  def initialize(arg1, arg2)    @arg1 = arg1    @arg2 = arg2  end
  def call  endend

The generated spec is the same as above.

Generate a namespaced service with arguments

$ rails generate service things/dothem arg1 arg2

# app/services/things/do_them.rbclass Things::DoThem  def self.call(arg1, arg2)    new(arg1, arg2).call  end
  def initialize(arg1, arg2)    @arg1 = arg1    @arg2 = arg2  end
  def call  endend

# spec/services/things/do_them_spec.rbrequire "rails_helper"
RSpec.describe Things::DoThem, type: :service do  pending "add some examples to (or delete) #{__FILE__}"end