Carrierwave Gem in Rails

Hi,

Carrierwave gem provides a flexible way to upload files from our Ruby applications. It is similar to paperclip gem in Rails 2.

Installing Carrierwave

We can install carrierwave gem using the following command.

$ gem  install  carrierwave

In our Rails application open the Gemfile and add the line

$ vi  Gemfile

gem  'carrierwave'

Using carrierwave

Example:

Create a Rails application where an candidate is applying for an job application.

$ rails new job_application
$ cd job_application
$ rails generate resource candidate name:string email:string phone:string skills:string qualification:string
$ rake db:migrate

We are now going to provide the candidate with option to upload the resume.

$ rails  generate  uploader  Resume

The above command will create a file resume_uploader.rb in app/uploaders/

In this file we can see something like below

resume_uploader.rb

class ResumeUploader < CarrierWave::Uploader::Base

storage :file

end

Add a string coloumn to the model where we want the uploader

t.string :resume

After adding this coloumn in migration drop and migrate the database.

Now mount the uploader in the model file.

class Candidate < ActiveRecord::Base

  mount_uploader :resume, ResumeUploader

end

In the form dont forget to set the html mutipart option to true for uploading the resume.

Now everything is done. We can now upload the resume.

Screenshots:

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Restricting User to upload only specified types of files

There is one more interesting option is there in carrierwave. We can restrict the type of the file to be uploaded.

Open the file app/uploaders/resume_uploader.rb

def extension_white_list
  %w(doc docx pdf odt)
end

We can provide the set of file types that can be uploaded. If the user tries to upload any file apart from what is provided in the extension white list method, then the carrierwave will not upload the file and it throws an error to the user.

Screenshot:

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The above is the simple example of how we can use carrierwave for uploading documents. I hope you found the above example useful for getting started and working with carrierwave.

For more information you can look at the following github documentation - https://github.com/jnicklas/carrierwave

Regards

Ramachandran

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