Rails - Aug 2006 - Array#chunk method, maybe someone will find this useful

class Array
  # break an array up into <size> 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

<table>
<% @photos.chunk(5).each do |pc| -%>
  <tr>
  <% pc.each do |p| -%>
    <td><%= p.nil? ? "Empty" : p.name -%></td>
  <% end -%>
  </tr>
<% end -%>
</table>

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

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.

On 8/12/06, Chris Hall <christopher.k.hall@gmail.com>
wrote:
>
> class Array
>   # break an array up into <size> 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
>
> <table>
> <% @photos.chunk(5).each do |pc| -%>
>   <tr>
>   <% pc.each do |p| -%>
>     <td><%= p.nil? ? "Empty" : p.name -%></td>
>   <% end -%>
>   </tr>
> <% end -%>
> </table>
>
> 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
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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Chris Hall wrote:
> class Array
>  # break an array up into <size> 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
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 Bini (http://ola-bini.blogspot.com)
  JvYAML, RbYAML, JRuby and Jatha contributor
  System Developer, Karolinska Institutet (http://www.ki.se)
  OLogix Consulting (http://www.ologix.com)

  "Yields falsehood when quined" yields falsehood when quined.