From: Brian Candler <b.candler@...>
Date: 2010-04-15T23:17:10+09:00
Subject: Re: Blocks and local variable creation

John Lane wrote:
> I have a simple method:
> 
> def rights_for_item (rights_hash, item)
>    rights_hash.each { |k,v| (rights ||= []) << k if v.include? item }
>    rights
> end
> 
> This does not work because "rights" is created local to the block on
> "rights_hash.each" instead of local to the method itself.

Just prepare it outside the block first:

def rights_for_item(...)
  rights = nil
  rights_hash.each { ... }
  rights
end

> But I don't think it is good idiomatic ruby code. Is there a better way
> to write this type of thing ?

It's arguably more idiomatic to return an empty array than to return 
nil. It's more consistent from the user's point of view. e.g. they can 
do

  if rights_for_item(x).include? "update"
    .. do something
  end

If there is a possibility of returning nil then it is more awkward:

  r = rights_for_item(x)
  if r && r.include? "update"
    .. do something
  end
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