DEV Community 👩‍💻👨‍💻

Ngari Ndung'u
Ngari Ndung'u

Posted on • Originally published at on

Last month I learnt - ruby can be weird

I was working on a task that involved parsing data from CSV files and saving it into rails models when I noticed something that didn’t look right. On calling to_json on one of the parsed csv rows, I got;

  "": null,
  "name": "John"

Enter fullscreen mode Exit fullscreen mode

For context, I was parsing the CSV using the headers: true option, and for some reason, I had an empty header. Since we all know that developers don’t make mistakes, it had to be an issue with the data. So, I went hunting.

Another lesson, if you’re looking for an issue with data, open it in it’s raw form. Opening the csv with LibreOffice Calc and choosing the helpful defaults, opened a perfectly good sheet, and surprise, no missing header! Just as I was about to concede that it might be me, I opened the file in my editor(vim) and despite the ugliness, the trailing comma on each line was hard to miss.

With a possible culprit found, it was back to the code to try and get rid of that entry. Q; which ruby type would result in an empty string in json? Now, if you use ruby I’d assume there’s literally no time you’ve wanted to use an empty string as a key in your hash, right? But still it get’s weirder, on calling to_h on the row;

  nil => nil,
  "name" => "John"

Enter fullscreen mode Exit fullscreen mode

What?! Yes, nil is a valid key in a ruby hash. I had to fire up plain irb to make sure it wasn’t rails messsing with me. And just to be sure, I confirmed that it’s also possible to retrieve the value normally with hsh[nil]

P.S If you ever find yourself needing to read json exported from mongo, BSON::ExtJSON.parse is your friend.

Top comments (1)

katafrakt profile image
Paweł Świątkowski

Well you can use any object as the key in the hash. Including nil, other hash or ActiveRecord object ;) That wouldn't be very performant, but it's technically possible.


Thank you.

Thanks for visiting DEV, we’ve worked really hard to cultivate this great community and would love to have you join us. If you’d like to create an account, you can sign up here.