How to know if i am in a module or in the main script?

ruby-talk
1

Hi all,

with ruby, it's possible to check if I am in the main script or in a
module with if __name__ == 'main'

Is there the same thing with ruby ?

Thanks

2

Stephane Wirtel wrote:

Hi all,

with ruby, it's possible to check if I am in the main script or in a
module with if __name__ == 'main'

Is there the same thing with ruby ?

Thanks

Here is a way to find if a ruby file is a module or the main script.

if $0 == __FILE__
  puts "This is the main function"
else
  puts "This is a module"
end

Is it right ?

3

Stephane Wirtel wrote:

if $0 == __FILE__
  puts "This is the main function"
else
  puts "This is a module"
end

Is it right ?

Yes, that is a very common idiom used by many Ruby programmers to
determine if the code is being included or 'run' by itself. Good job
figuring it out. :slight_smile:

4

Phrogz wrote:

Stephane Wirtel wrote:

if $0 == __FILE__
  puts "This is the main function"
else
  puts "This is a module"
end

Is it right ?

Yes, that is a very common idiom used by many Ruby programmers to
determine if the code is being included or 'run' by itself. Good job
figuring it out. :slight_smile:

Coincidentally, an idiom I don't like. Let libraries be libraries,
executables be executables (I prefer to use minimal "wire up" scripts
for my standalone apps, and keep the reusable bits in other files), and
test code be test code. Having a library test itself when "run" is a
common kludge I find rather pointless - not like your users ever need to
know test run results, it's the developer's responsibility to take care
of those. And it's the job of development tools to handle running tests
conveniently, not the programmer's by making his code indirectly depend
on its tests. (IIRC some RubyMate screencasts, that editor does seem to
have this thing covered.)

David Vallner

5

Yes, that is a very common idiom used by many Ruby programmers to
determine if the code is being included or 'run' by itself. Good job
figuring it out. :slight_smile:

Thanks

6

I don't know about Ruby, but many times this is used in Python libs to
run example code if it's being run by itself and just be a library if
it's included. Pretty neat way of keeping the file clutter to a
minimum.

--Jeremy

···

On 11/5/06, David Vallner <david@vallner.net> wrote:

Phrogz wrote:
> Stephane Wirtel wrote:
>> if $0 == __FILE__
>> puts "This is the main function"
>> else
>> puts "This is a module"
>> end
>>
>> Is it right ?
>
> Yes, that is a very common idiom used by many Ruby programmers to
> determine if the code is being included or 'run' by itself. Good job
> figuring it out. :slight_smile:
>

Coincidentally, an idiom I don't like. Let libraries be libraries,
executables be executables (I prefer to use minimal "wire up" scripts
for my standalone apps, and keep the reusable bits in other files), and
test code be test code. Having a library test itself when "run" is a
common kludge I find rather pointless - not like your users ever need to
know test run results, it's the developer's responsibility to take care
of those. And it's the job of development tools to handle running tests
conveniently, not the programmer's by making his code indirectly depend
on its tests. (IIRC some RubyMate screencasts, that editor does seem to
have this thing covered.)

David Vallner

7

Jeremy McAnally wrote:

I don't know about Ruby, but many times this is used in Python libs to
run example code if it's being run by itself and just be a library if
it's included. Pretty neat way of keeping the file clutter to a
minimum.

By cluttering the file internally with code not related to its main
purpose? I still claim laziness being the motive to not separate these
things, half-decent code browsing and project management tools / project
structuring conventions will negate any problems with finding code in
files anyway.

Either way, YMMV. I'll concede that this is more of a religious than
technical issue for me, stemming from my preference to separate concerns
as tidily as possible.

David Vallner

8

This is a good point in that this in not Ruby specific. I've seen this idiom in many languages for years now.

I like it and often use it to put a basic command-line interface over my libraries.

James Edward Gray II

···

On Nov 5, 2006, at 8:30 AM, Jeremy McAnally wrote:

I don't know about Ruby, but many times this is used in Python libs to
run example code if it's being run by itself and just be a library if
it's included. Pretty neat way of keeping the file clutter to a
minimum.

9

By cluttering the file internally with code not related to its main
purpose? I still claim laziness being the motive to not separate these
things,

Ah, but is laziness not one of the cardinal virtues?

Either way, YMMV. I'll concede that this is more of a religious than
technical issue for me, stemming from my preference to separate concerns
as tidily as possible.

"Separating concerns" sounds like a good principle, but I'd describe keeping test code in the library source file as "keeping related things together", which is an equally good principle. Now, in many cases it may be better, or even necessary, to keep tests separate from the code, but I think it makes a lot of sense to keep basic functionality tests in same source file as the module they're testing. I also first encountered this style in the Python community, and have come to like it. I especially like using this style when I first start writing a new module; later, when my modules become more mature and the tests get longer, I might migrate them out to separate files. It makes me happy to learn that Ruby supports this as well. (I don't think Perl does.)

TomP

···

On Nov 5, 2006, at 11:08 AM, David Vallner wrote: