How to Upload a File in Rails using CarrierWave

Uploading files in a Rails App is no sweet job now a days. Out of all the gems available in Rails Ecosystem, “CarrierWave” is widely used for its easy integration and flexibility to upload files.

Benefits

• File Caching: Prevents users to select the file again & re-upload if the form fails the validation process
• Clean Code: Helps to write all the logic in uploader classes rather than in models, keeping your model clean and readable
• Image Processing: Provides efficient way to resize & crop images to different formats
• Storage Support: Stores files in third party storages such as AWS S3 bucket, Racksapce or Google Cloud
• Mongodb: Has good support for mongodb with the help of “carrierwave-mongoid” gem

Setting Up CarrierWave
Step 1:
In your Rails App, add the following to your gem file & run the bundle installation.

[code language=”html”]
gem ‘carrierwave’
[/code]

Step 2:
Generate the uploader by running the following command:

[code language=”html”]
rails generate uploader Avatar
[/code]

It gives you a file in the path given below:

[code language=”html”]
app/uploaders/avatar_uploader.rb
[/code]

Here, “Avatar” is the column name.

Step 3:
Create a column to your model where you want to store the image:

[code language=”html”]
rails g migration add_avatar_to_students avatar:string
Rakedb:migrate
[/code]

Step 4:
Open up the model and mount the uploader:

[code language=”html”]
class Student < ActiveRecord::Base
mount_uploader:avatar, AvatarUploader
end
[/code]

Step 5:
In the generated uploader file you can mention different versions of an image, just like this:

[code language=”html”]
version :thumb do
process :resize_to_fill => [150, 150]
end
version :tiny_thumb do
process :resize_to_fill => [50, 50]
end
[/code]

Step 6:
Set file storage path in the uploader file. It’s the default storage path where all the files will be stored by CarrierWave.

[code language=”html”]
def store_dir
"uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
end
[/code]

Step 7:
Navigate to config > initializers and create a file: carrier_wave.rb.
Paste the following code:

[code language=”html”]
require ‘carrierwave/orm/activerecord’
[/code]

At this point, it loads CarrierWave after loading ActiveRecord.
You can also store the files into AWS S3 bucket by configuring in this way:

[code language=”html”]
CarrierWave.configure do |config|
config.fog_credentials = {
:provider => ‘AWS’,
: aws_access_key_id => "YOUR AMAZON ACCESS KEY",
:aws_secret_access_key => "YOUR AMAZON SECRET KEY",
:region => ‘us-west-1’ # Change this for different AWS region. Default is ‘us-east-1’
}
config.fog_directory = "bucket-name"
end
[/code]

Now, you should be able to upload files on the fly after reading this article.

Wrapping Up!

Faced any hiccups while uploading a file using CarrierWave? Write to me at info@andolasoft.com and I’ll try to find a way.

Also, I would appreciate if you leave your feedback/suggestions below.