From: Urban Hafner <the-master-of-bass@...>
Date: 2001-03-28T02:15:19+09:00
Subject: [ruby-talk:13240] hash problem

Hello everybody,
I've written a class that should create a simple database (like dbdbd of David
Alan Black, but I didn't quite understand it so I tried to write one on my own
to learn a bit more about ruby).

Here's a little script that uses this database:
# test.rb
require "UDB"

array = %w{Name Age Size Lines}
database = UDB.new(array)
hash = { "Name" => "Urban", "Age" => 19, "Size" => 1.73, "Lines" => 35 }
database.test
database.write(hash)
database.test
database.typeout

And here are the error is get:
$ ruby test.rb
key: Age  value: 1
key: Size  value: 2
key: Lines  value: 3
key: Name  value: 0
./UDB.rb:31:in `fetch': key not found (IndexError)
	from ./UDB.rb:31:in `write'
	from ./UDB.rb:29:in `each'
	from ./UDB.rb:29:in `write'
	from test.rb:10

Well,...
I think that the problem is somewhere, where I use the hashes @row and @index
but I don't know what I did wrong. 

Thanks for your help

Urban

--

class UDB
  def initialize(columnames)
    @columnames = columnames
    # The Database of this object
    @database = Array.new
    count = 0
    # Put all the columnames into the database
    @columnames.each do |name|
      @column = Array.new
      @column[0] = name
      @database[count] = @column
      count += 1
    end
    @index = {}
    count = 0
    # Register all the columns in a hash
    @database.each do |name|
      @index[name] = count
      count += 1
    end
  end
  def test
    @index.each { |key,value| print "key: ", key ,"  value: ", value, "\n" }
  end
  # Write new entry into the database
  def write(row)
    @row = row
    @row.each do |key,value|
      # Get Number of the column
      columno = @index.fetch(key)
      columno = columno.to_i
      # Make new entry
      @database[columno].push(value)
    end
  end
  # Write the database to stdout
  def typeout
    # Get number of rows
    0.upto(@database[0].length - 1) do |row|
      0.upto(@index.length - 1) do |column|
	print " #{@database[column][row]} "
      end
      print "\n"
    end
  end
end