From: Dave Thomas <Dave@...>
Date: 2002-03-27T23:21:56+09:00
Subject: Re: Hash.new(Hash.new) doesn't use Hash.new as default value

"Jonas Delfs" <jonas@NOSPAMdelfs.dk> writes:

> In the documentation for the 'new' method in the Hash class in Programming
> Ruby it says that 'anObject' will be used as default value, but consider the
> following example:
> 
> var = Hash.new(Hash.new)
> var['index1'] = 'value1'
> var['index2']['index22'] = 'value22'
> var['index3']['index32'] = 'value32'
> var['index4'] = 'value4'
> p var['donotexist']
> 
> Why does "p var['donotexist']" output {"index32" => "value32", "index22" =>
> "value22"} - and _not_ just {} (a new Hash)?
> If it's no bug, I think it's a bug in documentation. - and not a very logic
> behavior.

The default value is the hash created by Hash.new. There's just one of
these, which is the default value for all entries. As a result,
var['index2], var['index3'], and val['dontexist'] share it, which is
the effect you're seeing.


Dave