From: Rob Biedenharn <Rob@...>
Date: 2007-06-29T08:53:49+09:00
Subject: Re: newby non/programmer trying to understand classes

On Jun 28, 2007, at 6:45 PM, weathercoach@gmail.com wrote:
>    Hello.
> ...
>    I've scaled down my project to the most basic components that will
> still allow me to express my areas of confusion.    I have a file that
> changes daily which contains a list of people in this format
>
> bob.smith
> bill.johnson
> betty.joe
> tony.johnson
> wilbur.smith
>
>    Additionally I have a directory populated with 1 file per uniq last
> name (ie: smith, johnson, joe). I need to parse through the days list
> and then cleanse the last name files of the previous entries and
> insert the  updated list.

So when you're done, you have "==>filename<==" followed
by content lines like:

==>smith<==
bob.smith
wilbur.smith

==>johnson<==
bill.johnson

==>joe<==
betty.joe

Is there any reason that you can't wipe the directory clean (remove  
all the previous lastname files) when you start?

>   I've got the script that does this it is
> not very efficient (ie: i must define all the last names in
> advance).   So now i've started to rewrite the script and this is
> where I'm stuck
>
> ...
> nf = File.open("people", "r")
> surnames = []
>   nf.each_line do |l|
>     p = LastName.new(l)
>       sur = p.get_last
>       sur << l
>         surnames << sur
> end
>
> surnames.uniq.each do |s|
>   namefile = File.open(s,"w+")
>   namefile << s
> end
>
> ...

Let's translate the filename/content structure that you want to end  
with into a simple key/value hash:

{ "smith" => [ "bob.smith", "wilbur.smith" ],
   "johnson" => [ "bill.johnson" ],
   "joe" => [ "betty.joe" ]
}

...and then build that:

# create a Hash where referencing a non-existent
# key makes its value an empty Array
names = Hash.new { |h,k| h[k] = [] }

File.open('people', 'r') do |f|
   f.each do |name|
     name.chomp!  # remove the line-ending
     #    so "first.mi.last" will be ["first", "mi.last"]
     first_name, last_name = name.split('.', 2)
     names[last_name] << name
   end
end

>   Anyhoo I'd appreciate comments on my specific dynamic variable
> problem or any other pointers
> to help my get to the "AH HA!" moment with constructing and using
> classes which I feel I'm pretty close to.
>   TIA. G
>
>   ps:   I own many ruby books and have spent about 20 hours trying to
> solve this pretty basic situation and dont know where else to go for
> help.

Then you just need to create the output.  A simple way to
check in irb (you do use irb, right?) might be:

names.each {|last,ary| puts "#{last}:\n  #{ary.join("\n  ")}" }

But, if you need to remove all the existing files in the
directory and write out new ones, you'll want something like:

(note that I've assumed that the 'people' file and the script
itself live in a directory other than where you'll put the
lastname files [which is a subdirectory I called 'work'])

#!/usr/bin/env ruby -w
names = Hash.new { |h,k| h[k] = [] }

File.open('people', 'r') do |f|
   f.each do |name|
     name.chomp!
     #    so "first.mi.last" will be ["first", "mi.last"]
     first_name, last_name = name.split('.', 2)
     names[last_name] << name
   end
end

Dir.chdir('work') do |d|
   File.delete(*Dir['*'])
   names.each do |last,ary|
     File.open(last, 'w') do |lname|
       lname.puts ary.join("\n")
     end
   end
end

__END__


Now, that doesn't deal with a new class of your own making, but you  
don't really seem to need anything beyond some standard classes  
(Hash, Array, File, Dir).  This should give you plenty to think (and  
flip through your Pickaxe) about.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com