Types of Caching in Rails

A few types of caching to know :

• Page Caching: Save entire pages of an application without hitting the stack by returning cached pre-rendered pages. Good in applications without authentication and other highly dynamic aspects.
• Fragment Caching: Allows fragments of view logic, for example partials or other bits of HTML that are independent from other parts, to be wrapped in a cache block and served out of the cache store when the next request comes in.
• Action Caching: Works like Page Caching, except the incoming web request hits the Rails stack. This means that before filters (like authentication or other restrictions) can be run on it before the cache is served.
• Rails.cache: All cached content except cached pages are stored in the Rails.cache.
• HTTP Caching: HTTP caching occurs when the browser stores local copies of web resources for faster retrieval the next time the resource is required. It uses HTTP headers to determine if the browser can use a locally stored version of the response or if it needs to request a fresh copy from the server.

Uploading Multiple Images using CarrierWave

How to upload multiple image by selecting "ctrl + selction key" at same time.

CarrierWave
This gem provides a simple and extremely flexible way to upload files from Ruby applications.
This gem has convenient support for multiple file upload fields.

Following are the steps:

For Complete Source code click here

In Rails, add it to your Gemfile:

gem 'carrierwave'
 
bundle install
 
rails generate uploader photo

Create post scaffold

rails generate scaffold post title:string

Create post_attachment scaffold

post_attachment post_id:integer photo:string
 
rake db:migrate

In post.rb

class Post < ActiveRecord::Base
  has_many :post_attachments
  accepts_nested_attributes_for :post_attachments
end

In post_attachment.rb

class PostAttachment < ActiveRecord::Base
   mount_uploader :photo, PhotoUploader
   belongs_to :post
end

In post_controller.rb

def show
  @post_attachments = @post.post_attachments.all
end

 def new
   @post = Post.new
   @post_attachment = @post.post_attachments.build
 end
 
 def create
   @post = Post.new(post_params)
   respond_to do |format|
     if @post.save
       params[:post_attachments]['photo'].each do |a|
         @post_attachment = @post.post_attachments.create!(:photo => a)
       end
      format.html { redirect_to @post, notice: 'Post was successfully created.' }
     else
      format.html { render action: 'new' }
    end
   end 
 end
 
 private
  def post_params
    params.require(:post).permit(:title, post_attachments_attributes: [:id, :post_id, :photo])
  end

In views/posts/_form.html.haml

 = form_for(@post, :html => { :multipart => true }) do |f|
  .field
    = f.label :title
    = f.text_field :title
  = f.fields_for :post_attachments do |p|
    .field
      = p.label :photo
      = p.file_field :photo, :multiple => true, name: "post_attachments[photo][]"
  .actions
    = f.submit
 

In views/posts/show.html.haml

%p#notice= notice
%p
  %strong Title:
  = @post.title
- @post_attachments.each do |p|
  = image_tag p.photo_url
  = link_to "Edit Attachment", edit_post_attachment_path(p)
= link_to 'Edit', edit_post_path(@post)
|
\#{link_to 'Back', posts_path}
 

Update form to edit an attachment views/post_attachments/_form.html.haml

= image_tag @post_attachment.photo
= form_for(@post_attachment) do |f|
  .field
    = f.label :photo
    %br/
    = f.file_field :photo
  .actions
    = f.submit
 
 Now, update method in post_attachment_controller.rb

 def update
    respond_to do |format|
      if @post_attachment.update(post_attachment_params)
        format.html { redirect_to @post_attachment.post, notice: 'Post attachment was successfully updated.' }
      end
    end
  end

For Complete Source code click here