From: daz <dooby@...10.karoo.co.uk>
Date: 2003-09-26T15:24:49+09:00
Subject: Re: memory and storing references to data structures


"sdv" <foo@bar.com> wrote

> I want to hold data from structures in another array, modify the external
> structures  so that the array still refelects the changes: I've done as
> shown underneath but am i storing a 'reference' in the c/c++sense or am I
> duplicating data in the 'stuff' object? I dont wont to excessive memory
> usage.
>
> def main
> stuff=Hash::new()
> a1=['a','b','c']
> b1=['a','d','f']
> ll=nil
>
> ['a','b','c','d','e','f'].each {|i|
>   stuff[i]=Array::new()
>   }
>
> stuff['a'].push(a1)
> stuff['a'].push(b1)
> puts "#{stuff['a']}"
> a1[0]='foo'
> puts "#{stuff['a']}"
> end
>
> main


stuff=Hash[]

a1=['a','b','c']
b1=['a','d','f']

['a','b','c','d','e','f'].each {|i|
  stuff[i]=Array::new()
}

stuff['a'].push(a1)
stuff['a'].push(b1)
p stuff['a']
a1[0]='foo'
p stuff['a']

a1.size.times do |ix|
  p [ a1[ix], stuff['a'][0][ix] ]
  puts 'OK' if a1[ix].object_id == stuff['a'][0][ix].object_id
end


#-> [["a", "b", "c"], ["a", "d", "f"]]
#-> [["foo", "b", "c"], ["a", "d", "f"]]
#-> ["foo", "foo"]
#-> OK
#-> ["b", "b"]
#-> OK
#-> ["c", "c"]
#-> OK


Comparing object_id shows whether or not you're referring to
the same objects.
In your example, you are.


daz