Ruby: Sort an array of objects by an attribute

In this example I’ll show you how easy it is to sort an array of (the same kind of) objects by an attribute. Let’s say you have an array of User objects that have the attributes ‘name’ and ‘login_count’. First, find all users.

    @users = User.find(:all)

Now, we have to sort this array by ‘name’. Since we don’t know if any user used capitals in his name or not, we use ‘downcase’ to sort without case sensitivity.

A small not. ‘sort’ returns a new array and leaves the original unchanged. You may want to just reorder the @users array, so use the ‘sort!’ method. The ‘!’ indicates it’s a destructive method. It will overwrite the current @users array with the new sorting.

    @users.sort! { |a,b| <=> }

That’s all! Since strings are comparable, this will sort you user objects alphabetically by name. Want to sort on login_count instead?

    @users.sort! { |a,b| a.login_count <=> b.login_count }

So, now you can easily sort any object in an array just like you want it too!

I'd love to hear your questions and comments on this article! Mention @ariejan on twitter or shoot me an email.

About Ariejan

Hey! I'm a software engineer building rock solid back-end systems using Ruby, Ruby on Rails and Golang. In my free time I like to repair audio equipment, play the piano and experiment with electronics.