where_is_the_app.markdown

Where is the app?

This are different examples of doing the same thing, "mark a notification as read", and the pros and cons that I see in each example

1. - Logic in the model

• The user clicks the notification link
• The system POSTs to the action "notifications/:id/mark_as_read"
• The controller calls the method Notification#mark_as_read
• The model updates the attribute "read" saves the Notification record
• And sends the response back to the client

class App.NotificationView

  constructor: (@el, @notification) ->
    @el.click => @notification.markAsRead()
      
class App.Notification extends App.Model

  markAsRead: ->
    unless @get('read')
      $.ajax
        url: "notifications/#{@get 'id'}/mark_as_read"
        type: 'POST'
        dataType: "json"
        success: (json) =>
          @set('read', json.read)

class NotificationsController < ApplicationController
  def mark_as_read
    @notification = Notification.find(params[:id])
    @notification.mark_as_read
    return json: @notification
  end
end

class Notification < ActiveRecord::Base
  def mark_as_read
    update_attributes read: true
  end
end

Pros

• Logic in one place
• Can be part of a domain model in the server

Cons

• May be slow, because we have to wait to the server

2.- Logic in the controller

• The user clicks the notification link
• The client POSTs to the action "notifications/:id/mark_as_read"
• The controller updates the attribute "read" of the notification record and then saves it
• And sends the response back to the client

class App.NotificationView

  constructor: (@el, @notification) ->
    @el.click => @notification.markAsRead()
      
class App.Notification extends App.Model

  markAsRead: ->
    unless @get('read')
      $.ajax
        url: "notifications/#{@get 'id'}/mark_as_read"
        type: 'POST'
        dataType: "json"
        success: (json) =>
          @set('read', json.read)

class NotificationsController < ApplicationController
  def mark_as_read
    @notification = Notification.find(params[:id])
    @notification.update_attributes read: true
    return json: @notification
  end
end

Pros

• Logic that is only used in that case does not go in the model
• Looks like the controller serves only to call a method from the client

Cons

• May be slow because we have to wait to the server

3.- Logic in the client

• The user clicks the notification link
• The Notification#mark_as_read, method of a client model, that modifies the "read" attribute (backbone.js or something like that)
• The client updates to "notifications/:id" in the server

class App.NotificationView

  constructor: (@el, @notification) ->
    @el.click =>
      @notification.markAsRead()
      @notification.save()
      
class App.Notification extends App.Model

  markAsRead: ->
    @set('read', true)

class NotificaitiosController < ApplicationController
  def update
    @notification = Notification.find(params[:id])
    @notification.update_attributes(params[:notificaiton])
  end
end

Pros

• Logic in one place
• Can be part of a domain model in the client
• Fast, because we don`t wait to the server

Cons

• Not sure about business logic, in the client

4.- Logic client and server

• The user clicks the notification link
• The Notification#mark_as_read, method of a client model, that modifies the "read" attribute (backbone.js or something like that)
• The client POSTs to the action "notifications/:id/mark_as_read"
• The controller calls the method Notification#mark_as_read
• The model updates the attribute "read" and saves the Notification record
• And sends the response back to the client

class App.NotificationView

  constructor: (@el, @notification) ->
    @el.click => @notification.markAsRead()
      
class App.Notification extends App.Model

  markAsRead: ->
    @set('read', true)
    $.ajax
      url: "notifications/#{@get 'id'}/mark_as_read"
      type: 'POST'
      dataType: "json"
      success: (json) =>
        @set('read', json.read)

class NotificationsController < ApplicationController
  def mark_as_read
    @notification = Notification.find(params[:id])
    @notification.mark_as_read
    return json: @notification
  end
end

class Notification < ActiveRecord::Base
  def mark_as_read
    update_attributes read: true
  end
end

Pros

• Fast, because we don`t wait to the server

Cons

• Logic in many places
• Maybe a nightmare is comming