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At first it seemed alright. A little business logic in a controller or model wasn't going to hurt anything. Then one day you wake up and you're surrounded by fat models and unwieldy controllers. Curled up and crying in the corner, you can't help but wonder how it came to this.

Take back control. Slim down models and wrangle monstrous controller methods with ActiveInteraction.

Read more on the project page or check out the full documentation on


This project uses semantic versioning.

Add it to your Gemfile:

gem 'active_interaction', '~> 1.3'

And then execute:

$ bundle

Or install it yourself with:

$ gem install active_interaction

What do I get?

ActiveInteraction::Base lets you create interaction models. These models ensure that certain inputs are provided and that those inputs are in the format you want them in. If the inputs are valid it will call execute, store the return value of that method in result, and return an instance of your ActiveInteraction::Base subclass. Let's look at a simple example:

# Define an interaction that signs up a user.
class UserSignup < ActiveInteraction::Base
  # required
  string :email, :name

  # optional
  boolean :newsletter_subscribe, default: nil

  # ActiveRecord validations
  validates :email, format: EMAIL_REGEX

  # The execute method is called only if the inputs validate. It
  # does your business action. The return value will be stored in
  # `result`.
  def execute
    user = User.create!(email: email, name: name)
    if newsletter_subscribe
      NewsletterSubscriptions.create(email: email, user_id:

# In a controller action (for instance), you can run it:
def new
  @signup =

def create
  @signup =[:user])

  # Then check to see if it worked:
  if @signup.valid?
    redirect_to welcome_path(user_id:
    render action: :new

You may have noticed that ActiveInteraction::Base quacks like ActiveRecord::Base. It can use validations from your Rails application and check option validity with valid?. Any errors are added to errors which works exactly like an ActiveRecord model. By default, everything within the execute method is run in a transaction if ActiveRecord is available.

How do I call an interaction?

There are two way to call an interaction. Given UserSignup, you can do this:

outcome =
if outcome.valid?
  # Do something with outcome.result...
  # Do something with outcome.errors...

Or, you can do this:

result =!(params)
# Either returns the result of execute,
# or raises ActiveInteraction::InvalidInteractionError

What can I pass to an interaction?

Interactions only accept a Hash for run and run!.

# A user comments on an article
class CreateComment < ActiveInteraction::Base
  model :article, :user
  string :comment

  validates :comment, length: { maximum: 500 }

  def execute; ...; end

def somewhere
  outcome =
    comment: params[:comment],
    article: Article.find(params[:article_id]),
    user: current_user

How do I define an interaction?

  1. Subclass ActiveInteraction::Base

    class YourInteraction < ActiveInteraction::Base
      # ...
  2. Define your attributes:

    string :name, :state
    integer :age
    boolean :is_special
    model :account
    array :tags, default: nil do
    hash :prefs, default: nil do
      boolean :smoking
      boolean :view
    date :arrives_on, default: -> { Date.current }
    date :departs_on, default: -> { Date.tomorrow }
  3. Use any additional validations you need:

    validates :name, length: { maximum: 10 }
    validates :state, inclusion: { in: %w(AL AK AR ... WY) }
    validate :arrives_before_departs
    def arrive_before_departs
      if departs_on <= arrives_on
        errors.add(:departs_on, 'must come after the arrival time')
  4. Define your execute method. It can return whatever you like:

    def execute
      record = do_thing(...)
      # ...

Check out the documentation for a full list of methods.

How do I compose interactions?

You can run interactions from within other interactions by calling compose. If the interaction is successful, it'll return the result (just like if you had called it with run!). If something went wrong, execution will halt immediately and the errors will be moved onto the caller.

class AddThree < ActiveInteraction::Base
  integer :x
  def execute
    compose(Add, x: x, y: 3)
end!(x: 5)
# => 8

To bring in filters from another interaction, use import_filters. Combined with inputs, delegating to another interaction is a piece of cake.

class AddAndDouble < ActiveInteraction::Base
  import_filters Add
  def execute
    compose(Add, inputs) * 2

How do I translate an interaction?

ActiveInteraction is i18n-aware out of the box! All you have to do is add translations to your project. In Rails, they typically go into config/locales. So, for example, let's say that (for whatever reason) you want to print out everything backwards. Simply add translations for ActiveInteraction to your hsilgne locale:

# config/locales/hsilgne.yml
      array: yarra
      boolean: naeloob
      date: etad
      date_time: emit etad
      decimal: lamiced
      file: elif
      float: taolf
      hash: hsah
      integer: regetni
      model: ledom
      string: gnirts
      time: emit
        invalid: dilavni si
        invalid_type: '%{type} dilav a ton si'
        missing: deriuqer si

Then set your locale and run an interaction like normal:

I18n.locale = :hsilgne
class Interaction < ActiveInteraction::Base
  boolean :a
  def execute; end
# => {:a=>["deriuqer si"]}


ActiveInteraction is brought to you by @AaronLasseigne and @tfausak from @orgsync. We were inspired by the fantastic work done in Mutations.