Adding a file upload feature to an app is fairly simple with the popular Carrierwave gem. And commercial file hosting is seamless as well with Amazon’s Simple Storage Service (S3), which plays very nicely with Carrierwave. I’ll cover S3 integration in a later post.
I’ve broken down the process into 3 easy steps:
1. Add a file upload field in your view and a column to your model
The first step is to implement a file upload field in a form on your app:
form_for .... do
= f.file_field :passport_picture
f.submit "Submit"
You need a column called “passport_picture” in your model, so generate a migration and add in that column.
We used a popular gem called Carrierwave to handle the file uploading, so let’s add it and its associated gems to the Gemfile:
gem 'carrierwave'
gem "fog", "~> 1.3.1"
gem 'mini_magick'
2. Make uploader classes for each file
Now we need to make an uploader class that contains uploading instructions. Our uploader will instruct Carrierwave to use the MiniMagick gem for image processing (optional):
app/uploaders/passport_picture_uploader.rb
class PassportPictureUploader < CarrierWave::Uploader::Base
include CarrierWave::MiniMagick
store: file
process :resize_to_fill => [200, 200]
end
One caveat here: you need to make sure ImageMagick is installed on your computer, and this was not easy for me. You can install it using Homebrew or Rvm if you don’t have it, but google around for more specific instructions.
3. Mount the uploaders in your model
Now you need to tell your model to mount the uploader(s):
class User < ActiveRecord::Base
mount_uploader :passport_picture, PassportPictureUploader
end
And that’s it!
As an aside, I think this would be a good candidate to shuffle off to a background process so that the user doesn’t have to wait until the file uploads for the form to submit. I’ll talk about what I’ve learned about background processes in a later post.
ZenOnRails 