I read an article this morning on TechCrunch about an upcoming service that makes it easy for developers to add mobile logins to their web applications, and I thought I’d try something similar for a new project I’m working on.
If you use the Devise gem for managing logins for your Rails app, and
you pass the :token_authenticatable to the devise method, then your
users can log in with a link that includes an authentication token,
bypassing the email/username and password login. With that in place,
all you need to do is generate a QR code that encodes a link to your app
with this authentication token included. Here’s how you can do that:
Following the instructions of the qr code gem,
install the gem by adding gem 'rqrcode' to your Gemfile and running
bundle install. Generating the code can be done in a HAML view like so:
- qr = RQRCode::QRCode.new(root_url(Devise.token_authentication_key => current_user.authentication_token), :size => 10, :level => :l)
%table
- qr.modules.each_index do |x|
%tr
- qr.modules.each_index do |y|
%td{ class: qr.dark?(x,y) ? 'black' : 'white' }/
This assumes that you have devise hooked into your User model, and the currently-logged in user is available to the view via the current_user method. Using the CSS from the rQRCode home page, this will display a QR code that can be scanned on a phone.
This will allow a user to log in to your app (using their laptop), scan the QR code on their phone, and then be logged in on their mobile browser. Easy. :)
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