From: David Alan Black <dblack@...>
Date: 2002-02-24T11:27:19+09:00
Subject: Re: Newbie question

Hello --

On Sun, 24 Feb 2002, roktas wrote:

> $FMT = "/\t/"
>
> # Only one hash for the field labels (not 2*n)
> $labels = {}
>
> def parse_line(line, fmt=$FMT)
>     # No extra process for the present
>     line.chomp.strip(delim)
> end
>
> def DB
>     def initialize(f)
>         # First create the $labels hash from the first line
>         $labels = ...
>
>         # Other stuff filling the @tab array
>         ...
>     end
>
>     ...
>
>     def [](key)
>         @tab[key]
>     end
> end
>
> def Record < Array
>     def initialize(line)
>         # Parse and create a new record
>         parse_line(line)
>     end
>     def [](key)
>         key if key.kind_of?Integer
>         $labels.index(key) if key.kind_of?String
>         # Raise something for invalid cases ?
>     end
> end
>
> Well... (1) I don't want to use any global var ($labels), (2) Seperating
> 'records' and 'whole database' (DB) would be fine.

I'm not sure about (2).  Somehow the Record has to know about the
fields in the database.  Here's one way to do it with relatively
little overhead -- each Record has an instance variable which points
to the relevant fields array (but doesn't duplicate that array).


  class TSDB < Array
    attr_reader :labels, :records
    SEP = "\t"

    def TSDB.parse_line(line, sep=SEP)
      line.chomp.strip.split(/#{sep}/)
    end

    class Record < Array
      attr_accessor :fields

      def initialize(line)
	concat(TSDB.parse_line(line))
      end

      def [](key)
	at(@fields.index(key))
      end
    end

    def initialize(f)
      fh = File.open(f, "r")
      @fields = TSDB.parse_line(fh.readline)
      push("Dummy 0th record")
      concat (fh.readlines.map do |line|
	  r = Record.new(line)
	  r.fields = @fields
	  r
      end)
    end
  end

  # Based on same tsd.txt file as last time:
  t = TSDB.new("tsd.txt")
  p t[1]["field1"]        # "one"
  p t[2]["field2"]        # "orange"



David

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