Rails - Mar 2006 - how to access a hash within a hash in ruby?

Simple question:

I know how to access a data field in a hash by doing 
hash_name[datafield_name].

But what if the datafield itself is a hash? I tried a couple of 
variations but nothing seems to be working and tutorials do not go into 
such details.

Is there a simple way or should I create separate instances?

-Chris



-- 
Posted via http://www.ruby-forum.com/.

Chris Brown wrote:
> Simple question:
> 
> I know how to access a data field in a hash by doing 
> hash_name[datafield_name].
> 
> But what if the datafield itself is a hash?

hash_name[datafield_name][key_name]

-Brian

Chris Brown wrote:
> 
> Simple question:
> 
> I know how to access a data field in a hash by doing 
> hash_name[datafield_name].
> 
> But what if the datafield itself is a hash? I tried a couple of 
> variations but nothing seems to be working and tutorials do not go into 
> such details.
> 
> Is there a simple way or should I create separate instances?
> 
> -Chris
Hi,

you''re not saying what you tried and maybe I missed your point but:
h = {"h1" => {"h2" => "hello"}}
h["h1"]["h2"]
gives "hello" :)

--
Agnieszka

-- 
Posted via http://www.ruby-forum.com/.

Thanks, Agnieszka. I didn''t know I could do this but I''m not
sure it
will work in my case. My_hash contains standard data of an RSS file: 
channel_title, channel URl and items. Items contains: title, link, 
author and description.

so My_hash[''title''] returns the right RSS channel Title e.g.
CNN To
stories

But how can I return only all the links? or only one description? I''m 
not familiar with hashes so I''m confused.

My_hash[''items''][link] does not work as you suggested below.


 Figiel wrote:
> Chris Brown wrote:
>> 
>> Simple question:
>> 
>> I know how to access a data field in a hash by doing 
>> hash_name[datafield_name].
>> 
>> But what if the datafield itself is a hash? I tried a couple of 
>> variations but nothing seems to be working and tutorials do not go into
>> such details.
>> 
>> Is there a simple way or should I create separate instances?
>> 
>> -Chris
> 
> Hi,
> 
> you''re not saying what you tried and maybe I missed your point
but:
> h = {"h1" => {"h2" => "hello"}}
> h["h1"]["h2"]
> gives "hello" :)
> 
> --
> Agnieszka

-- 
Posted via http://www.ruby-forum.com/.

On Friday 31 Mar 2006 21:50, Chris Brown wrote:
> My_hash[''items''][link] does not work as you suggested
below.
Try:

My_hash[''items''][''link'']

You missed the quotes on ''link''...?

~Dave

-- 

Dave Silvester
Rent-A-Monkey Website Development
http://www.rentamonkey.com/

PGP Key: http://www.rentamonkey.com/pgpkey.asc

Hi Chris,

Chris Brown wrote:
> My_hash contains standard data of an RSS file:
> channel_title, channel URl and items.
> Items contains: title, link, author and description.
>
> so My_hash[''title''] returns the right RSS channel
> Title e.g. CNN To stories
>
> But how can I return only all the links? or only one
> description? I''m not familiar with hashes so I''m
confused.
I just had to work through this a week or so ago (accessing a hash of
hashes, not the RSS part) so I''ll pass along what I learned in the hope
it
will help.

In general, a hash is a set of (key, value) pairs.  The value can be a
singleton value, another hash, an array...  Those values can, themselves, be
any of the same.  To access a values in a multi-level hash, you iterate
through the levels.  So conditionally accessing a hash of hashes looks
like...

level1.each do |level1_key, level1_value|   # iterate through the top level
set of pairs
  if level1_key == what_you_want            # test each key to see if you
want to process it''s values
    level1_value.each do |level2_key, level2_value|  # if you do, and
it''s a
hash itself, iterate through it
      if level2_key == another_thing_you_want  # test each key to see if ...
        level2_value.each do |level2_key, level3_value|  # and so on
           # and down you go...
        end
      end
    end
  end
end

HTH,
Bill

Chris
    > I''m not familiar with hashes so I''m confused.

When in doubt, I always :
1/ check the online doc:
     http://www.ruby-doc.org/core/classes/Hash.html

2/ experiment on tryruby.
     tryruby.hobix.com/

You should also master Array and Enumerable iterations methods (reject, 
inject, collect, etc..)

Alain