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comp.lang.ruby

FILE test

raving_ruby_rider

2/21/2006 2:53:00 PM

I noticed that a lot of scripts apply the following coding pattern:

if __FILE__ == $0
....
end

I know what is does but what kind of problems does it solve?

thx,

used-to-be-a-Smalltalker
7 Answers

James Gray

2/21/2006 3:17:00 PM

0

On Feb 21, 2006, at 8:58 AM, raving_ruby_rider wrote:

> I noticed that a lot of scripts apply the following coding pattern:
>
> if __FILE__ == $0
> ....
> end
>
> I know what is does but what kind of problems does it solve?

It allows the file to be both a library (when required the if
statement will not run) and executable.

Hope that helps.

James Edward Gray II

Peter Hickman

2/21/2006 3:23:00 PM

0

You will see this sort of thing in other scripting languages. __FILE__
contains the name of the file source file and $0 is the name of the
currently executing script. So a file called hello.rb

class Hello
def initialize(name)
@name = name
end

def greet
puts "Hello #{@name}"
end
end

if __FILE__ == $0 then
h = Hello.new('World')
h.greet
end

you can then run this file with ruby hello.rb which will run the code at
the bottom. However with tom.rb

require 'hello'

h = Hello.new('tom')
h.greet

when you run tom.rb the __FILE__ == $0 part of hello does not run as the
file hello.rb but the currently executing script is tom.rb. This allows
you to have a ruby file hold the class for inclusion by other scripts
and also be a utility script in it's own right.

Vassilis Rizopoulos

2/21/2006 7:25:00 PM

0

Peter Hickman wrote:
> You will see this sort of thing in other scripting languages. __FILE__
> contains the name of the file source file and $0 is the name of the
> currently executing script. So a file called hello.rb
>
...
> when you run tom.rb the __FILE__ == $0 part of hello does not run as the
> file hello.rb but the currently executing script is tom.rb. This allows
> you to have a ruby file hold the class for inclusion by other scripts
> and also be a utility script in it's own right.
>
Not to mention the fact that it allows you to easily write unit tests
for most of the code in a script.
V.-

--
http://www.braveworl...

____________________________________________________________________
http://www.f... - äùñåÜí õðçñåóßá çëåêôñïíéêïý ôá÷õäñïìåßïõ.
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David Vallner

2/22/2006 1:13:00 AM

0

Dna Utorok 21 Február 2006 20:25 Damphyr napísal:
> Peter Hickman wrote:
> > You will see this sort of thing in other scripting languages. __FILE__
> > contains the name of the file source file and $0 is the name of the
> > currently executing script. So a file called hello.rb
>
> ...
>
> > when you run tom.rb the __FILE__ == $0 part of hello does not run as the
> > file hello.rb but the currently executing script is tom.rb. This allows
> > you to have a ruby file hold the class for inclusion by other scripts
> > and also be a utility script in it's own right.
>
> Not to mention the fact that it allows you to easily write unit tests
> for most of the code in a script.
>

Which I personally can't bear the sight of. Library is script is test? Nuh-uh.
Just my two cents.

David Vallner

Adam Shelly

2/22/2006 8:01:00 PM

0

On 2/21/06, David Vallner <david@vallner.net> wrote:
> Which I personally can't bear the sight of. Library is script is test? Nuh-uh.

So what is the 'ruby way' to store your unit tests? A separate require'd file?

James Byrne

2/22/2006 9:14:00 PM

0

Adam Shelly wrote:

> So what is the 'ruby way' to store your unit tests? A separate
> require'd file?

Well, going by the Pickaxe book you end up with something like this:

/classfilename
->/doc
->/lib
->/test

in ./classfilename/lib you create your ruby source file classfilename.rb
in ./classfilename/test you create your ruby test/unit file
classfilename_tc.rb

In classfilename_tc.rb you put the following lines at the start:

#----------------------------------------------------------------
# The following prefixes ../lib to the active ruby load path
$:.unshift File.join(File.dirname(__FILE__), "..", "lib")

require 'test/unit'
require 'classfilename'

class Test_ClassFileName < Test::Unit::TestCase
...
#----------------------------------------------------------------

and then write your test cases as methods. When you run your test suite
you can invoke it from any palce on the system as the #unshift prefixes
the load path with the relative location of the classfilename.rb with
respect to the test case file.

Thus, assuming that for the example given above that ./ = ~/ruby then:

#ruby -w ~/ruby/classfilename/test/classfilename_tc.rb

will work whatever pwd you are in.

I love test/unit...

Regards,
Jim

--
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Vassilis Rizopoulos

2/23/2006 3:19:00 PM

0

David Vallner wrote:
> Dna Utorok 21 Február 2006 20:25 Damphyr napísal:
>> Peter Hickman wrote:
>>> You will see this sort of thing in other scripting languages. __FILE__
>>> contains the name of the file source file and $0 is the name of the
>>> currently executing script. So a file called hello.rb
>> ...
>>
>>> when you run tom.rb the __FILE__ == $0 part of hello does not run as the
>>> file hello.rb but the currently executing script is tom.rb. This allows
>>> you to have a ruby file hold the class for inclusion by other scripts
>>> and also be a utility script in it's own right.
>> Not to mention the fact that it allows you to easily write unit tests
>> for most of the code in a script.
>>
>
> Which I personally can't bear the sight of. Library is script is test? Nuh-uh.
> Just my two cents.
Well I actually put the unit tests in a different file.
The if $0==__FILE__ check allows me to require the script in the unit
test file.
Following mostly the DRY principle and having a knack for organizing
code allows you to group most of the functionality in objects (at which
point you put them in a 'library' file and forget about it) or methods
to be used by the 'top-level' script. Requiring the 'script' file allows
me to unit test the methods without contriving manual tests.
I found it most valuable when I do parameter parsing and
parameter/configuration validation in my command line scripts.
Cheers,
V.-

--
http://www.braveworl...

____________________________________________________________________
http://www.f... - ?????? ???????? ???????????? ????????????.
http://www.f... - free email service for the Greek-speaking.