From: Edmond Kachale <kachaleedmond@...>
Date: 2011-10-25T22:50:21+09:00
Subject: Unusual behavior of a Ruby hash

--0016362845e403323704b01fd204
Content-Type: text/plain; charset=ISO-8859-1

Rubysters,

I had the following code working nicely:

(a) http://pastie.org/private/8qn4f36mfeppbobm7b2wsa

At the beginning of every iteration, I expect "essential_params" hash (in
line 8) to look like this: essential_params  = {:val_1 => 0, :val_2 =>
[x,y,z], :val_3 =>0}. However it does repetitive work to initialize a hash
from a database (in line 8).

So as to reduce repetitive database querying (at every iteration), I have
just moved hash initialization to (line 7) outside a loop:

(b) http://pastie.org/private/iudfe0q2s41vszxby6vva

Now the code acts wierd: At every iteration,  my "essential_params" hash
contains data accumulated from the previous iterations. For example, at the
nth iteration, essential_params may look like this: {:val_1 => 25, :val_2 =>
[x,y,z], :val_3 =>24} which are results from (n-1)th iteration (instead of
the default values: {:val_1 => 0, :val_2 => [x,y,z], :val_3 =>0}).

Does anyone have a better explanation about this? Are Ruby hashed assigned
by value or by reference? (Specifically, why is the pre-populated hash at
line 7 in (b) getting values from lines 22 and 23 ? )

Kind regards,

*--
Edmond*

--0016362845e403323704b01fd204--