From: matt@... (matt neuburg)
Date: 2008-05-09T11:25:03+09:00
Subject: Re: How to re-replace Hash default value behaviour?

Siep Korteling <s.korteling@gmail.com> wrote:

> Hash.new(0) and the block form of Hash.new{_smart_stuff_}  come in
> really handy while reading in a hash.
> When the reading is done however, my hash serves to provide data. At
> that stage, the default_value behaviour gets in the way. For instance,
> if the hash contains the number of goals for soccerplayers, I don't want
> the hash to return value "0" for the key "Wolfgang Amadeus Mozart"; by
> then I want plain old Nil, or "No data available".
> 
> failed experiment:
> 
> Class Hash
>   def default_proc
>     Nil
>   end
> end
> 
> How can Hash.new behaviour be changed?
> 
> regards,
> Siep

h = Hash.new.merge(h)

So for example:

h = Hash.new(0)
h[:a] += 2
h[:a] += 1
h[:b] += 4
p h #=> {:a=>3, :b=>4}

h = Hash.new.merge(h)
p h[:c] #=> nil, it's now returning plain old nil

m.
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