QR Code Ruby

In this project, we’ll write a command-line program that generates QR code images. We’ll be using a gem called rqrcode to do most of the heavy lifting for us¹.

Explore the target

There is a solution in the file called solution.rb. To see how it behaves, first we must install the rqrcode gem. At a command prompt:

gem install rqrcode

Then, run the solution (ruby solution.rb) to explore how your program should work. (Don’t peek at the solution code until you’ve tried some things on your own.)

You should notice a few things about the final solution:

• The program gives you four options: to generate QR codes for URLs, wifi networks, and text messages; and to exit the program.
• If you select 4, the program ends.
• If you select 1, 2, or 3, the program creates a PNG file that contains a QR code.
• Try typing in an option that the program doesn’t expect (i.e., not 1, 2, 3, or 4); how does it handle it?

Hello world

Create a file to write the program in. I called mine qr.rb.

Add some code to print “hello world” and ensure that you can run the program without any issues.

At a command prompt, bin/server. Visit /git and make a commit. Push your changes back to GitHub.

Keep the /git page open in a tab. As you work, continue to make commits and push them.

Install the rqrcode gem

To get access to the rqrcode gem, at a command prompt:

gem install rqrcode

Using the rqrcode gem

The rqrcode gem has a lot of different options² for rendering QR codes — as PNG files, as <svg> elements, and more.

For now, we’re going to render PNG images only. To do so, here’s how it works:

require "rqrcode"

# Use the RQRCode::QRCode class to encode some text
qrcode = RQRCode::QRCode.new("wikipedia qr code")

# Use the .as_png method to create a 500 pixels by 500 pixels image
png = qrcode.as_png({ :size => 500 })

# Write the image data to a file
IO.binwrite("sometext.png", png.to_s)

Try adding the above code to your program and run it. You should see a file pop up in your file tree called sometext.png.

If you open that file and scan it with your phone’s camera, it should offer to search for the text we encoded. Neat!

Encoding URLs

If you provide a fully-qualified URL as the text to be encoded (starting with https or http) then most phones will offer to take you directly to the URL when the QR code is scanned. Try updating your code with a URL instead:

qrcode = RQRCode::QRCode.new("https://en.wikipedia.org/wiki/QR_code")

Try scanning the generated image with your phone. Did it work?

Join a wifi network

If you want the QR code to automatically join a wifi network, then you must encode text in the following format:

WIFI:T:WPA;S:My wifi network;P:supersecretpassword;;

In the above example, My wifi network is the name of the network to be joined, and supersecretpassword is the password for that network. Replace them with the actual network name and password that you want to generate a QR code for.

Give it a try. Did the generated image work?

Send a text message

If you want the QR code to pre-populate a text message, then you must encode text in the following format:

SMSTO:9876543210:Hi Alice! It's

• No spaces are allowed in the phone number.
• You can include country codes, e.g. +19876543210.

In the above example, when the QR code is scanned it will open the messages app with the message Hi Alice! It's and phone number (987) 654-3210 pre-filled.

Give it a try. Did the generated image work?

Suggested steps

Before reading further, you can and should attempt to write the program on your own. How can you break the program down into tiny little steps?

Once you get stuck (that might not take long), then read on for some suggestions:

Make the program interactive

Write some code that prompts the user to enter a URL of their choice.

Then use their input to generate the QR code dynamically.

Give your user options

Write some code that first prompts the user to select whether they want a URL, wifi network, or text message to be encoded in the QR code.

Depending on their selection, prompt them further for the information you need to generate the QR code.

Then use their input to generate the QR code dynamically.

Stretch goal: make the program loop until exited

Optionally, write some code that will keep generating QR codes until the user chooses to exit.

The while, next, and break keywords might come in handy. Read more here.

To submit

Submit the URL of your GitHub repository. You can keep pushing up commits after the due date in case you add more features.

• QR Code Ruby
  • Explore the target
  • Hello world
  • Install the rqrcode gem
  • Using the rqrcode gem
  • Encoding URLs
  • Join a wifi network
  • Send a text message
  • Suggested steps
    • Make the program interactive
    • Give your user options
    • Stretch goal: make the program loop until exited
  • To submit