Problem #

  • Presentation (View) logic does not belong in a model!
  • app/helpers/users_helper is as global as app/helpers/application_helper… Why?!
  • code from app/helpers is auto-included in views, but not controllers/models

Solution: #

  • Use gem draper’s decorators to separate presentation logic and call it when needed

Example: #

1 - BAD # 

/app/models/user.rb

  def username
    return name if name.present?
    email.split('@')[0]
  end

# or

/app/helpers/users_helper.rb

  def username
    return name if name.present?
    email.split('@')[0]
  end

2 - GOOD # 

/app/decorators/user_decorator.rb

  def username
    return name if name.present?
    email.split('@')[0]
  end

Installation #

Gemfile

  gem 'draper'

console

bundle
rails generate draper:install
rails generate decorator User

Getting generators to work: #

initialize the decorator in a controller:

# app/controllers/users_controller.rb

  def index
    @users = User.all.decorate
  end

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

OR more complex - with pagy and ransack:

# app/controllers/users_controller.rb

  def index
    @q = User.all.ransack(params[:q])
    @pagy, @users = pagy(@q.result(distinct: true)
    @users = @users.decorate
  end

Now you can call (in a view):

  <%= @user.username %>

OR decorate a signle call (in a view):

  <%= current_user.decorate.username %>

Example of calling associations, decorating a price:

app/decorators/user_decorator.rb

class PostDecorator < Draper::Decorator
  # belongs_to :user
  # has_many :comments

  delegate_all

  decorates_association :user, with: UserDecorator
  decorates_association :comments #, with: CommentDecorator

  def price
    h.number_to_currency(price, precision: 0)
  end
end

More real-life usage examples coming later.

Useful Resources: