From: Daniel Harple <dharple@...>
Date: 2006-06-06T05:16:06+09:00
Subject: Re: Object Troubles - undefined method `+'

On Jun 5, 2006, at 10:00 PM, Paul D. Kraus wrote:
> When i run the below program I get this error...
> ./parse.rb:14:in `incndainvoice': undefined method `+' for  
> nil:NilClass
> (NoMethodError)
>        from ./parse.rb:31
>        from ./parse.rb:20
>
>    def increment_invoice
>        invoices = invoices + 1
>    end
>    def increment_ndainvoice
>        ndainvoice = ndainvoice + 1
>    end

You are trying to set local variables. Instance variables are  
prefixed with @. If you were trying to call your attr_writer method,  
you need to prefix it with self:

self.invoices += 1

Here is a more idiomatic way of writing what you would like:

class Customer
   attr_accessor :invoices, :ndainvoices
   def initialize
     @invoices = 0
     @ndainvoices = 0
   end
end

customers = Hash.new { |h, k| h[k] = Customer.new }
IO.foreach('NdaInvoiceCount.txt') do |line|
   (customer_code, ship_method, customer_name) = line.chomp.split('|')
   customers[customer_code].invoices += 1
   customers[ customer_code ].ndainvoices += 1 if ship_method ==  
'SAVGRD'
end

-- Daniel