Rails 4 multiple image or file upload using carrierwave-open source projects carrierwaveuploader/carrierwave

This is solution to upload multiple images using carrierwave in rails 4 from scratch

Or you can find working demo : Multiple Attachment Rails 4

To do just follow these steps.

rails new multiple_image_upload_carrierwave

In gem file

gem 'carrierwave'
bundle install
rails generate uploader Avatar 

Create post scaffold

rails generate scaffold post title:string

Create post_attachment scaffold

rails generate scaffold post_attachment post_id:integer avatar: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 :avatar, AvatarUploader
   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]['avatar'].each do |a|
          @post_attachment = @post.post_attachments.create!(:avatar => a, :post_id => @post.id)
       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, :avatar])
   end

In views/posts/_form.html.erb

 { :multipart => true }) do |f| %>
   
     

     
   

   
     
       

        true, name: "post_attachments[avatar][]" %>
     
   

   
     
   

To edit an attachment and list of attachment for any post. In views/posts/show.html.erb

  Title:
  





  
  


 |

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

Modify 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

In rails 3 no need to define strong parameters and as you can define attribute_accessible in both the model and accept_nested_attribute to post model because attribute accessible is deprecated in rails 4.

For edit an attachment we cant modify all the attachments at a time. so we will replace attachment one by one, or you can modify as per your rule, Here I just show you how to update any attachment.