Tag: Rails

Integrating Trailblazer and ActiveRecord transactions outside of a request lifecycle

April 27, 2016 /

When you use Ruby on Rails with ActiveRecord, you can get used to having separate transaction on each request. This is valid also when using Trailblazer (when inside of a request scope), however Trailblazer on its own does not provide such functionality. It means that when you're using it from the console and/or when you process stuff inside background workers, you no longer have an active transaction wrapping around an operation.

This behavior is good most of the time. Since background tasks can run for a long period of time, there might be a risk of unintentional locking a big part of your database. However, sometimes you just need to have transactions.

In order to provide this feature for each operation, we will use a concern that will include that logic. We will also make it configurable, so if we inherit from a given operation, we will still have an option to disable/enable transaction support based on the operation requirements.

The code itself is pretty simple - it will just wraps around a #run method of the operation class with a transaction (as long as transaction support is enabled). Note, that by default transactional flag is set to false.

module Concerns
  module Transactional
    extend ActiveSupport::Concern

    included do
      class_attribute :transactional

      self.transactional = false
    end

    def run
      if self.class.transactional
        self.class.transaction do
          super
        end
      else
        super
      end
    end

    class_methods do
      def transaction
        ActiveRecord::Base.transaction do
          return yield
        end
      end
    end
  end
end

In order to use it, just include it into your operation:

class ApplicationOperation < Trailblazer::Operation
  # Including on its own won't turn transactions on
  include Concerns::Transactional
end

class DataOperation < ApplicationOperation
  # This operation will have a single transaction wrapping it around
  self.transactional = true
end

Rails + Responders + Trailblazer – Flash messages with proper model names from Trailblazer operations

February 29, 2016 /

Responders gem is really awesome. It sets flash message based on the controller action and resource status allowing you to dry up your Rails controllers. Trailblazer is a thin layer on top of Rails. It gently enforces encapsulation, an intuitive code structure and gives you an object-oriented architecture. When combining both of them together, you can achieve really slim and functional controllers:

class ContractsController < BaseController
  def index
    respond_with(collection Contracts::Index)
  end

  def show
    respond_with(present Contracts::Update)
  end

  def new
    respond_with(form Contracts::Create)
  end

  def create
    respond_with(run Contracts::Create)
  end

  def edit
    respond_with(form Contracts::Update)
  end

  def update
    respond_with(run Contracts::Update)
  end

  def destroy
    respond_with(run Contracts::Destroy)
  end
end

Unfortunately there's one downside: Since Responders #respond_with method expects a model as a first argument, it will think that your operation is a model (if you return it the way I did) and try to figure out it's human name. Probably it won't end up as you expect and you will see a message similar to this one:

Users/campaigns/update was successfully updated.

It happens because of this piece of code from Responders:

resource_name = if resource.class.respond_to?(:model_name)
  resource.class.model_name.human
else
  resource.class.name.underscore.humanize
end

Trailblazer operations don't respond to #model_name, that's why all the operations will be translated using the else statement. To make it work as expected, we just need to implement the #model_name class method:

class ApplicationOperation < Trailblazer::Operation
  def self.model_name
    ::ActiveModel::Name.new(model_class)
  end
end

I follow the ApplicationController, ApplicationRecord, ApplicationHelper "pattern" also with operations. That way I don't need to add this code into Trailblazer::Operation or into each of the operations separately. #model_class method is a method that will return the model class that we've set using Trailblazer::Operation #method:

class Operation < ApplicationOperation
 include Model
 model Contract
end

Operation.model_class #=> Contract
Operation.model_name #=> ActiveModel::Name:0x0000000575b778 @name="Contract"...

From now on, all the Trailblazer operations will introduce themselves to Responders with the name of the model on which we operate.

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