---
layout: programming
title:  "ruby 2.6+ array#difference"
date:  2019-02-05 
categories: programming
---

# Array#Difference - [Array#Difference](https://github.com/ruby/ruby/blob/trunk/array.c#L4450-L4563)
I wanted to do a quick post on a new method added to ruby Array class in version 2.6. I just learned about this over the past weekend. 
This will quickly grow to be a favorite of mine.

A method to check differences in values between two arrays.

#### Make arrays abc and abcdef

{% highlight ruby %}
[1] pry(main)> abc = ['a','b','c'] 
=> ["a", "b", "c"]

[2] pry(main)> abcdef = ['a', 'b', 'c', 'd', 'e', 'f']
=> ["a", "b", "c", "d", "e", "f"]
{% endhighlight %}


<hr>


#### Ruby 2.5
In versions prior, I would make a .difference method in my .pryrc file and that
will be loaded at runtime when I run my console. You can also monkey patch it
live in a pry console. Found this via
[stackedoverflow](https://stackoverflow.com/questions/8639857/rails-3-how-to-get-the-difference-between-two-arrays)
post. Here is how I would add it in a running pry session: 

{% highlight ruby %}
[17] pry(main)> class Array
[17] pry(main)*   def difference(a)
[17] pry(main)*     self - a | a - self
[17] pry(main)*   end  
[17] pry(main)* end  
=> :difference

[26] pry(main)> abcdef.difference(abc)
=> ["d", "e", "f"]

{% endhighlight %}


<hr>


#### Ruby 2.6
But now in ruby 2.6+, you can just use the .difference method. It is built into
the class now.

{% highlight ruby %}
[3] pry(main)> abcdef.difference(abc)
=> ["d", "e", "f"]
{% endhighlight %}

So nice, so easy!