Presenter Vs Decorator Vs Helpers In Rails

Introduction

In Rails, helpers, presenters, and decorators are design patterns for organizing view logic, making views cleaner and more maintainable. All three extend the functionality of models and controllers, but they are slightly different in their way.

Let’s walk through examples of using a helper, presenter, and decorator to handle the same task: displaying a user’s full name and their formatted signup date.

Using Helper

1. Model

class User < ApplicationRecord
  # attributes: first_name, last_name, created_at
end

2. Helper

module UserHelper
  def full_name(user)
    "#{user.first_name} #{user.last_name}"
  end

  def date_format(user)
    user.created_at.strftime("%Y-%m-%d")
  end
end

3. Controller

def show
  @user = User.find(params[:id])
end

4. View

<%= date_format(@user) %>
<%= full_name(@user) %>

Using Presenter

app/presenters/users_presenter.rb

1. Presenter

class UsersPresenter
  def initialize(user)
    @user = user
  end

  def full_name
    "#{@user.first_name} #{@user.last_name}"
  end

  def sign_up_date
    @user.created_at.strftime("%Y-%m-%d")
  end
end

2. Controller

def show
  @user = User.find(params[:id])
  @user_presenter = UsersPresenter.new(@user)
end

3. View

<%= @user_presenter.full_name %>
<%= @user_presenter.sign_up_date %>

Using a Decorator (with Draper Gem)

app/decorators/user_decorator.rb

1. Decorator

class UserDecorator < Draper::Decorator
  delegate_all

  def full_name
    "#{object.first_name} #{object.last_name}"
  end

  def sign_up_date
    object.created_at.strftime("%Y-%m-%d")
  end
end

2. Controller

def show
  @user = User.find(params[:id]).decorate
end

3. View

<%= @user.full_name %>
<%= @user.sign_up_date %>

Comparison of Use Cases

When to Use Which

Conclusion

Each approach has strengths. Helpers are great for simple, reusable logic, Presenters encapsulate complex view logic and multiple models, and Decorators extend model instances with view-specific methods. Choose the pattern that matches the complexity and structure of your application’s view logic.