gl-command

GL::Command

GL::Command is an implementation of the Command Pattern to encapsulate business logic.

The idea is to avoid bloat in Controllers and reduce coupling between models.

Installation

Add the following line to your Gemfile:

gem 'gl-command'

Download and install the gem:

bundle install

Interface

Basic use case

class SomeController
  def index
    result = DoComplexCommand.call
  end
end

class DoComplexCommand
  include GL::Command

  def call
    ... complex business logic ...
  end
end

Providing data

The call method accepts a hash of parameters as context. The Command has access to these parameters via the the context attribute.

class SomeController
  def index
    result = DoComplexCommand.call(page: params[:page],
                                   sort: params[:sort])
  end
end

class DoComplexCommand
  include GL::Command

  def call
    BusinessObject.method_call(offset: context.page * 50,
                               ordering_by: context.sort)
    ... complex business logic ...
  end
end

Returning data

The parameters of the call method get converted into a GL::Context.

class SomeController
  def index
    result = DoComplexCommand.call(page: params[:page],
                                   sort: params[:sort])
    @business_data = result.bunsiness_result
  end
end

class DoComplexCommand
  include GL::Command

  def call
    context.business_result = BusinessObject.method_call(offset: context.page * 50,
                                                         ordering_by: context.sort)
  end
end

Failure and success

Should the business logic not be successful, a Context can be failed via context.fail!. The context comes with an errors of type ActiveModel::Errors.

class SomeController
  def index
    result = DoComplexCommand.call(page: params[:page],
                                   sort: params[:sort])
    @business_data = result.bunsiness_result
    render and return if result.success?
    render_failure if result.failure?
  end
end

class DoComplexCommand
  include GL::Command

  def call
    context.business_result = BusinessObject.method_call(offset: context.page * 50,
                                                         ordering_by: context.sort)
    if business_result.blank?
       context.errors.add(:base, 'no data found.')
       context.fail!
    end
  end
end

Should an exception occur, the interactor fails automatically and adds exception details to context.errors.

class DoComplexCommand
  include GL::Command

  def call
    raise StandardError
  end
end

Rollback

Whenever a GL::Command fails, it executes rollback if defined.

class DoComplexCommand
  include GL::Command

  def call
    # change a lot of things
    raise StandardError
  end

  def rollback
    # undo all the changes
  end
end

Hooks

GL::Commands offer before, around, and after hooks.

class DoComplexCommand
  include GL::Command

  before :initialize_logger
  around :measure_time
  after :close_transaction

  def call
    context.business_result = BusinessObject.method_call(offset: context.page * 50,
                                                         ordering_by: context.sort)
    if business_result.blank?
       context.errors.add(:base, 'no data found.')
       context.fail!
    end
  end

  private

  def initialize_logger
    # initialize logger
  end
  def measure_time
    time = Time.now
    call
    duration = Time.now - time
  end
  def close_transaction
    # closing transaction
  end
end