From: Christer Nilsson <janchrister.nilsson@...>
Date: 2006-09-09T17:41:55+09:00
Subject: How to read and write 80 column punched cards with Ruby

I'm trying to communicate with a bank. Banks are still using the punched 
card layout in their files.

Example: 001234567800023420060909
(account=12345678, amount=234 and day=20060909)

I'm trying to make some nice Ruby classes to handle this.

I would like to define the class like this (compare attr)

class Trans < Record
  field :account, 10
  field :amount, 6
  field :lastday, 8
end

This is what I've been able to do:
(There are several problems: As the fields have to be in a certain order 
a hash will not work. On the other hand, looping through an array takes 
time. Another is the problem of setting an attribute to nil, 
trans.account=nil)

class Field
  attr_accessor :name, :size, :pad, :value
  def initialize(name,size,pad)
    @name=name
    @size=size
    @pad=pad
  end
end

class Record
  def initialize
    @fields = []
  end
  def field name, size, pad
    @fields << Field.new(name.to_s, size, pad)
  end
  def save s
    p=0
    @fields.each do |f|
      f.value = s[p,f.size]
      p += f.size
    end
  end
  def to_s
    s=""
    @fields.each do |f|
      s += f.value.to_s
    end
    s
  end
  def method_missing(id, value=nil)
    if value==nil then
      @fields.each do |f|
        return f.value if f.name == id.to_s
      end
    else
      x = id.to_s.gsub("=", "")
      @fields.each do |f|
        f.value = value if f.name == x
      end
    end
  end
end

class Trans < Record
  def initialize
    super
    field :account, 10
    field :amount, 6
    field :lastday, 8
  end
end

trans = Trans.new
trans.save "001234567800023420060909"

puts trans.account
trans.amount = 120
puts trans

/Christer

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