From: Foo <foo@...>
Date: 2004-07-17T23:07:13+09:00
Subject: Having Trouble with IO.popen example

Hi-

I am new to ruby and I am reading the SAMS "Teach yourself Ruby in 21 
days" book.  I've gotten to the part where the book discusses the 
operating system and Ruby.  I'm having trouble with an example in the 
book and was hoping someone could help.  The script is spinnertest.rb:

#!/usr/bin/env ruby

require 'spinner2'  # Edit this line for different spinners

# Our slow recursive Fibonacci function.
def fib(n) (n<=2) ? 1 : (fib(n-2)+fib(n-1)) end

print "Please wait while I calculate a large Fibonacci number. "

animation = Spinner.new
result = fib(28)
animation.stop

puts
puts result


The class is called spinner2.rb:

class Spinner
    Baton = '\|/-'
    def initilaize
        STDOUT.flush
        @child = IO.popen('-', 'w+')
        if @child.nil?
            rotation = 0
            until select([$stdin], nil, nil, 0.2)
                STDERR.printf "%c\b", Baton[(rotation+=1) &3]
            end
            gets #read the 'stop' message
            STDERR.printf " \b" # erase the last Baton character
            exit!
        end
    end
    
    def stop
        @child.puts("stop yer rotation") # message content is unimportant
        @child.close
    end
end

When I run spinnertest.rb I get a blank screen for awhile, then after 
the calculation is complete I get the following:

../spinner2.rb:18:in `stop': private method `puts' called for 
nil:NilClass (NoMethodError)
        from ./spinnertest.rb:12
Please wait while I calculate a large Fibonacci number. 

I am guessing that ruby is having trouble with 'puts' being used this 
way, but I do not understand why, nor, how to fix it.  Can someone 
please help me with this item?

:)Thanks.

SA