# Nuby question regarding classes and ARGV

**URL:** <https://www.ruby-forum.com/t/nuby-question-regarding-classes-and-argv/80235>\
**Category:** Ruby\
**Created:** [December 22, 2006, 6:48pm UTC](https://www.ruby-forum.com/t/nuby-question-regarding-classes-and-argv/80235 "2006-12-22T18:48:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jasonmorrison](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/47e85d/32.png) [@jasonmorrison](https://www.ruby-forum.com/u/jasonmorrison)\
**Post date:** [December 22, 2006, 6:48pm UTC](https://www.ruby-forum.com/t/nuby-question-regarding-classes-and-argv/80235/1 "2006-12-22T18:48:06Z")

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I just took a program that works using a command line argument and  
turned it  
into a class so that I could require it from . Anyway, I was just  
wondering  
how you would pass somethign to it now as an argument.

if the syntax of the original program was ‘ruby program.rb Jason’ and  
the  
program did stuff with ‘Jason’, how would I go about making another  
program  
(a GUI for example) pass along information into that program as an  
argument? I can’t seem to get this to work. I’ve tried variants of the  
following:  
psuedo code (saved as program2.rb):  
‘require program.rb’  
b = ‘Jason’  
a = ClassNameInProgram.new(b)  
a = ClassNameInProgram.new {b}  
a = ClassNameInProgram.new b

If I run ‘ruby program2.rb Jason’, I get the same output as if I’d run ’  
program.rb Jason’. What am I not doing correctly? Hopefully I’ve  
explained  
this adequately and hopefully I’m not being incredibly stupid.

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<div class="post-metadata">

**Author:** ![jasonmorrison](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/47e85d/32.png) [@jasonmorrison](https://www.ruby-forum.com/u/jasonmorrison)\
**Post date:** [December 22, 2006, 7:02pm UTC](https://www.ruby-forum.com/t/nuby-question-regarding-classes-and-argv/80235/2 "2006-12-22T19:02:08Z")

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On 12/22/06, Jason M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> ‘require program.rb’  
> b = ‘Jason’  
> a = ClassNameInProgram.new(b)  
> a = ClassNameInProgram.new {b}  
> a = ClassNameInProgram.new b
> 
> If I run ‘ruby program2.rb Jason’, I get the same output as if I’d run ’  
> program.rb Jason’. What am I not doing correctly? Hopefully I’ve explained  
> this adequately and hopefully I’m not being incredibly stupid.

1. if you have

class ClassName…  
def initialize  
…ARGV[0]…  
end  
end

turn it into

class ClassName…  
def initialize(\*argv)  
…argv[0]…  
end  
end

or

class ClassName…  
def initialize(arg0, arg1, arg2)  
…arg0…  
end  
end

1. you can have both varieties:

do the above changes and  
at the very end of the file put the following:

if **FILE** == $0  
ClassName…new(\*ARGV)  
end

* * *

Notes:  
A bit safer way is to write  
if File.expand( **FILE** ) == File.expand($0)  
to handle program.rb vs ./program.rb cases

\*ARGV “expands” the ARGV array as the actual parameters to new.  
I.e. it is the same as calling new(ARGV[0], ARGV[1],…) It’s a handy  
trick,  
that can be used in case statements as well. (arr = [1,2,3], … when  
\*arr)

1. In the case of wrapping a script I usually split the code into  
initialization (new/initialize) and actual processing  
(run/process/whatever).