Ruby Tips I learned While Building an API From Scratch

Some of the lessons I learned while writing our new API from scratch in Ruby and Padrino

Part 1

Find unique values inside an array of hashes based on a value

Say you have an array of hashes and want to remove duplicates based on 1 key, that’s easy you do:

    array.uniq { |e| e[:key_name] }

For example, consider the following array of hashes:

array = [{:name=>"Yes, Yes, Yes", :artist=>"Some Dude", :duration=>"3:21"},
{:name=>"Chick on the Side", :artist=>"Another Dude"},
{:name=>"Luv Is"},
{:name=>"Yes, Yes, Yes", :artist=>"Some Dude"},
{:name=>"Chick on the Side", :artist=>"Another Dude", :duration=>"2:20"},
{:name=>"new one", :composer=>"compo"}]

These are tracks in an album, but the array could be of anything. So if we wanted to remove any duplicate tracks by name, we’d do:

    array.uniq { |e| e[:name] }

This would return only unique entries based on the :name value.

But what happens when you need to determine uniqueness by more than one key? No problem, uniq can take a block as you can see in the above example, the trick is knowing how to write that block.

In our case, we want to keep uniq values based on name, artist and composer so we would do this:

    array.uniq { |a_track| [ a_track[:name], a_track[:artist], a_track[:composer] ] }

It’s the same as the first example but using more than one criteria, nice!

Continuing with hashes, what if you need to store hashes in a file for some reason? Maybe you’re running some tests and want a quick way to store the results, or maybe you need to store some data in an ordered manner but don’t want to overhead of a database. Whatever the case, there is an easy way to store hashes in a file.

Storing hashes in a file