From: lasitha <lasitha.ranatunga@...>
Date: 2009-03-25T20:15:16+09:00
Subject: Re: creating an array by reusing code

On Wed, Mar 25, 2009 at 4:12 PM, Sijo Kg <sijo@maxxion.com> wrote:
> [...]
>   Now i need to create an array of size 12 containing record counts for
> month January to December like [recordcountjanuary,recordcountfeb,....]
> So for the first month january I tried like
>
> all_req.select do |r|
>  r.created_at.mon == 1
> end
>       What i need is reuse the above code I have placed it in a
> function But there I have to call it 12 times .How can i avoid this?

Let's build this up a step at a time...

monthly_counts = (1..12).map do |month|
  # call your function here, passing in the month
end

Depending on the scope of all_req, it may just be easier to inline the
function as follows:

monthly_counts = (1..12).map do |month|
  all_req.select {|r| r.created_at.mon == month }.size
end

However, this is inefficient.  We have to make 12 passes over the
all_req collection.
You can, instead use Enumerable#group_by:

all_req.group_by {|r| r.created_at.mon }

which will return a hash of items keyed by the month.  Getting counts
from this is simply a matter of using #map.  I'll leave this as an
exercise :)

Now, having said all that, the most efficient way to do this is
probably to use a group_by clause in your finder.  Again, left as an
exercise (mostly 'cos i don't know AR :)

solidarity,
lasitha