# Array#chunk method, maybe someone will find this useful

**URL:** <https://www.ruby-forum.com/t/array-chunk-method-maybe-someone-will-find-this-useful/102427>\
**Category:** Rails\
**Created:** [August 15, 2006, 2:17pm UTC](https://www.ruby-forum.com/t/array-chunk-method-maybe-someone-will-find-this-useful/102427 "2006-08-15T14:17:14Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![bigdaddy71](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bbe5ce/32.png) [@bigdaddy71](https://www.ruby-forum.com/u/bigdaddy71)\
**Post date:** [August 15, 2006, 2:17pm UTC](https://www.ruby-forum.com/t/array-chunk-method-maybe-someone-will-find-this-useful/102427/1 "2006-08-15T14:17:14Z")

</div>

class Array

# break an array up into chunks

def chunk(size=1)  
return self if self.empty?  
raise ArgumentError if !size.kind\_of? Integer

```
y = self.length.divmod(size)
rows = (y[1] > 0) ? y[0] + 1 : y[0]
arr = Array.new(rows)
(0...rows).each do |i|
  arr[i] = self.slice(size*i, size)
end

(arr.last.length...size).each { |i| arr.last[i] = nil } if

```

arr.last.length \< size  
arr  
end  
end

put it in /lib and add require ‘array’ at the end of environment.rb  
and restart and you should be good to go.

have you ever found yourself trying to loop through an activerecord  
result array and determine how to handle displaying a specific # of  
items per row and what to do when you have an odd number of elements  
on the last row? it can get ugly.

Array.chunk might be for you.

this method takes an array and breaks it out into smaller subarrays of  
a specified size.

@photos = Photo.find(:all).

say you had 12 photos returned…chunk would break your array of  
photos up into ‘chunks’ of 5 elements each adding nil objects to fill  
in the empty elements, so you would end up with

[[p1, p2, p3, p4, p5], [p6, p7, p8, p9, p10], [p11, p12, nil, nil, nil]]

then in your view you could do

\<% @photos.chunk(5).each do |pc| -%\> \<% pc.each do |p| -%\> \<% end -%\> \<% end -%\>

| \<%= p.nil? ? "Empty" : p.name -%\> |

note: i’ve only done rudimentary testing by hand in irb and console.  
so your mileage may vary. if it needs a license, then MIT.

Chris

---

<div class="post-metadata">

**Author:** ![bigdaddy71](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bbe5ce/32.png) [@bigdaddy71](https://www.ruby-forum.com/u/bigdaddy71)\
**Post date:** [August 15, 2006, 2:18pm UTC](https://www.ruby-forum.com/t/array-chunk-method-maybe-someone-will-find-this-useful/102427/2 "2006-08-15T14:18:54Z")

</div>

Chris H. wrote:

> ```
> arr[i] = self.slice(size*i, size)
> 
> ```
> 
> end
> 
> (arr.last.length…size).each { |i| arr.last[i] = nil } if  
> arr.last.length \< size  
> arr  
> end  
> end

Have you ever seen each\_slice?

require ‘enumerator’

[1,2,3,4,5,6,7,8].each\_slice {|a,b,c| puts a,b,c}  
1,2,3  
4,5,6  
7,8,nil

–  
Ola B. ([http://ola-bini.blogspot.com](http://ola-bini.blogspot.com))  
JvYAML, RbYAML, JRuby and Jatha contributor  
System Developer, Karolinska Institutet ([http://www.ki.se](http://www.ki.se))  
OLogix Consulting ([http://www.ologix.com](http://www.ologix.com))

“Yields falsehood when quined” yields falsehood when quined.

---

<div class="post-metadata">

**Author:** ![bigdaddy71](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/bbe5ce/32.png) [@bigdaddy71](https://www.ruby-forum.com/u/bigdaddy71)\
**Post date:** [August 15, 2006, 2:19pm UTC](https://www.ruby-forum.com/t/array-chunk-method-maybe-someone-will-find-this-useful/102427/3 "2006-08-15T14:19:33Z")

</div>

Rails already has this actually:

[1,2,3,4,5,6,7,8].in\_groups\_of(3) =\> [[1, 2, 3], [4, 5, 6], [7, 8, nil]]

-Jonathan.