One big reason to pick ActiveInteraction to implement Command pattern in Rails apps over rolling you own solution using Virtus and ActiveModel::Model

active_interaction.rb

class Foo < ActiveInteraction::Base
  string :bar

  # additional validations
  # validates :bar, ...
  
  def execute
    unless do_something
      errors.add :bar, 'is not cool'
    end
  end

  def do_something
    false
  end
end

command = Foo.run(bar: nil)
command.valid? #=> false
command.errors.full_messages
#=> ["Bar is required"]

command = Foo.run(bar: 'test')
command.valid? #=> false
command.errors.full_messages
#=> ["Bar is not cool"]

# Therefore..

command = Foo.run(bar: 'test')
if command.valid?
  redirect_to root_path
else
  render :new
end

virtus.rb

class Foo 
  include Virtus.model
  include ActiveModel::Model

  attribute :bar, String

  # This validation needs to be here since Virtus does 
  # not require attributes to be present be default
  validates :bar, presence: true
  
  def execute
    unless do_something
      errors.add :bar, 'is not cool'
    end
  end

  def do_something
    false
  end
end

command = Foo.new(bar: nil)
command.valid? #=> false
command.errors.full_messages
#=> ["Bar can't be blank"]
 
command = Foo.new(bar: 'test')
command.valid? #=> true (!!!)
command.execute
command.valid? #=> false
command.errors.full_messages
#=> ["Bar is not cool"]

# Therefore..

command = Foo.new(bar: 'test')
# Runs ActiveModel validations..
if command.valid?
  command.execute
  
  # Still valid after execute? (!!!)
  if command.valid?
    redirect_to root_path
  else
    render :new
  end
end