From: Michael Fellinger <m.fellinger@...>
Date: 2010-12-31T19:32:16+09:00
Subject: Re: a common idiom

On Fri, Dec 31, 2010 at 7:12 PM, Michel Demazure <michel@demazure.com> wrote:
> I often have to write something like
>
> some_enumerator.collect ... # or collect.with_index ...
> ....
> next if ...
> ...
> end.reject(&:nil?)
>
> Is there a better way to do a "collect_unless_nil", avoiding the double
> processing ?
> _md

For one, you can use #compact instead of #reject.
The way I'd do it is:

results = []
some.each do |value|
  results << value.operation if value.condition?
end

And then you could also use inject, which is a bit harder to grasp at
a glance and a bit more wordy, but some people believe you should
avoid variables outside of blocks at all costs... even if you end up
assigning the results to one.

some.inject [] do |results, value|
  next results unless value.condition?
  results << value.operation
end

Also, at least since 1.9, you can use `some.each_with_index` or
`some.to_enum.with_index.inject`.

-- 
Michael Fellinger
CTO, The Rubyists, LLC