From: David Alan Black <dblack@...>
Date: 2002-02-24T07:01:25+09:00
Subject: Re: Newbie question

Hello --

On Sun, 24 Feb 2002, roktas wrote:

> Hi all,
>
> How can I create an array of array with some funny (!) properties? To
> make clear, here is the exact problem: I have a tab seperated text file
> which the first line points to the field labels, that is;
>
> field1\tfield2\tfield3
> foo\tbar\tgoo
> ..
>
> I have created a 'DB' class which holds the whole data (after some
> parsing). What I want to realize is something that results with the
> following simple calls in the main block:
>
> db = DB.new("file.txt")
> p db[3]["field2"]
>
> I have some experimental codes but don't include them to prevent messing
> around. Inside a 'Record' class (inherited from Array), I have played
> with [] method to take a string argument (like "field2" as shown above)
> and used this class as the line container in a base array, but can't
> succeed :(

What you want, I think, is an array of hashes.  Each hash would
represent one line from your data file.

Here's a little example, data file first then program file.  It first
grabs the first line from the file, and gets the field names from it.
Then it reads the other lines; for each one, it creates a hash (with
the field names as keys and the values from the line as values), and
pushes that hash onto the TSDB object itself.

# tsd.txt (tab-separated):
field1	field2	field3
one	two	three
apple	orange	banana

# tsd.rb:
class TSDB < Array

  def initialize(file)
    concat ["Dummy 0'th element"]  # so that you can index from 1
    fh = File.open(file, "r")
    fields = fh.readline.chomp.split(/\t/)

    fh.readlines.each do |line|
      data = line.chomp.split(/\t/)
      record = {}
      fields.each_with_index {|f,i| record[f] = data[i]}
      push(record)
    end
  end
end

t = TSDB.new("tsd.txt")
p t[1]["field1"]          # =>  "one"
p t[2]["field2"]          # =>  "orange"

__END__


Since t[1] is a hash, you can get at its values with strings (i.e., its
keys are strings).


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav