Proposed Interactor 4.0 Syntax

place_order.rb

class PlaceOrder
  include Interactor
  
  # What goes here?
  
  before do
    context.user ||= User.find(context.user_id)
  end
  
  def call
    context.order = context.user.orders.create(context.attributes)
    
    context.fail! unless context.order.persisted?
  end
end

IMO the following is easier to read and reason about, but that may just my bias since I've been thinking along these lines recently:

class PlaceOrder
  include Interactor

  expects :user_id, :attributes

  allows(:user) do
    User.find(user_id)
  end

  provides(:order) do
    user.orders.create(attributes)
  end

  def call
    context.fail! unless order.persisted?
  end
end

Heck, I'd even like to do away with the call and any reference to context and replace it with something like:

fails_on(error: "Order not persisted") { !order.persisted? }