From: Cary Swoveland <cary@...>
Date: 2010-01-18T05:56:13+09:00
Subject: Newbie needs help getting started

I have just written the code for my first Ruby program, one that finds
the shortest path from start to finish in a maze.  All i/o is through
files and a terminal.  I have now turned to debugging it.  To help me, I
have the books, "The Ruby Programming Language" and "Ruby Cookbook", and
of course vast internet resources.  I'm using Ruby 1.8.7 on a MacBook. I
need a few answers to help me get started.

1. Is this the normal way to debug a program: with a terminal window
open, save changes to the x.rb file in an editor, and enter

ruby "filename" args

in the terminal? (Presumable, using a Ruby IDE is another alternative.
I've also noted how irb works.)  If "yes", does the execution begin with
the first statement that is outside a class definition (as there seems
to be nothing comparable to C's main(), for example)?

2. Suppose I've defined two classes, C1 and C2, a "main" program and
some methods that are outside class definitions.  Assume there is a
statement

c1 = C1.new

in a class C2 method and

c2 = c2.new

in a method outside the two classes.  In the file containing my code,
maze_problem.rb, do these blocks of code have to be placed in any
particular order?

3. I ran

ruby maze_problem.rb

in the terminal and got the following error message:

undefined method `[]=' for nil:NilClass

with no reference to where in maze_problem.rb the problem occurred.  How
do I go about finding the source of this error?

Many thanks.

Cary
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