8parth

# user.rb
# simple
has_many :posts, dependent: :destroy # all posts
has_many :published_posts, -> { where(published: true) }, class_name: "Post" # all published posts

# advanced
has_many :comments, through: :posts,  dependent: :destroy
has_many :comments_on_published_posts, through: :published_posts, dependent: :destroy # comments on published posts

8parth

ddb = Aws::DynamoDB::Client.new({
  access_key_id: '',
  secret_access_key: '',
  region: ''
})
# or, if you want to connect to local dynamodb database,
ddb = Aws::DynamoDB::Client.new(endpoint: 'http://localhost:8000')

# suppose table is created with following partition_key and range_key,
# partition_key => "partition_key"

8parth

class UserMailer < ApplicationMailer
  default from: "[email protected]"

  def welcome(email, name, message)
    @email = email
    @name = name
    @message = message

    mail to: @email, subject: "Welcome to Example."
  end

8parth

UserMailer.welcome("[email protected]", "xyz", "some message").deliver_later

8parth

class UserMailer < ApplicationMailer
  before_action {
    @email = params[:email]
    @name = params[:name]
    @message = params[:message]
  }

  default to: -> { @email },
          from: -> { "[email protected]" }

8parth

UserMailer.with(email: "[email protected]", name: "xyz", message: "some message").welcome.deliver_later

8parth

<%= form_for(@category) do |f| %>
  <% if f.object.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(f.object.errors.count, "error") %> prohibited this category from being saved:</h2>
      <ul>
      <% f.object.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>

8parth

# we are saving data to category and subcategory models
<%= form_with(model: @category) do |f| %>
  # instead, we can simply pass url, along with scopes if necessary
  # <%= form_with(scope: :category, url: category_path) %>
  <% if f.object.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(f.object.errors.count, "error") %> prohibited this category from being saved:</h2>
      <ul>
      <% f.object.errors.full_messages.each do |message| %>
        <li><%= message %></li>

8parth

class Song
  include ActiveModel::Model, ActiveModel::Serialization
  
  attr_accessor :name
  attr_accessor :movie_ids
  attr_accessor :created_at
  attr_accessor :updated_at
  
  def self.migrate_table
    migration = Aws::Record::TableMigration.new(self)

8parth

class User < ApplicationRecord
  # rails 4 way of defining virtual attribute
  attr_accessor :full_name
  
  # new rails 5 way of defining virtual attributes with datatype and default values
  attribute :name, :string, default: -> {  "No Name" }
  attribute :age, :float, default: 99

  before_save :assign_name
  before_save :assign_full_name