# Calling method defined in ruby script from external world

**URL:** <https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591>\
**Category:** Ruby\
**Created:** [September 5, 2006, 2:08pm UTC](https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591 "2006-09-05T14:08:21Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Saumya\_D](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/eada6e/32.png) [@Saumya\_D](https://www.ruby-forum.com/u/Saumya_D)\
**Post date:** [September 5, 2006, 2:08pm UTC](https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591/1 "2006-09-05T14:08:21Z")

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How can we make C routine call a “method” defined in a ruby script ?  
I am familiar with extending ruby to call C routines with/without swig.  
But I was not able to find a easy solution for it. The only way it may  
workout is spawning the script in a different process/thread from C code  
and  
then make it do all query/answer sequence by calling a C routine. Is  
there a  
easy way out?  
Can’t we make a C routine call a specific method in a Ruby Script.

Can we access a C stack from Ruby or vice versa while debugging the  
Ruby  
extension.

Regards,  
Saumzy.

---

<div class="post-metadata">

**Author:** ![Saumya\_D](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/eada6e/32.png) [@Saumya\_D](https://www.ruby-forum.com/u/Saumya_D)\
**Post date:** [September 5, 2006, 4:22pm UTC](https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591/2 "2006-09-05T16:22:50Z")

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On 9/5/06, Saumya D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> How can we make C routine call a “method” defined in a ruby script ?  
> I am familiar with extending ruby to call C routines with/without swig.  
> But I was not able to find a easy solution for it. The only way it may  
> workout is spawning the script in a different process/thread from C code and  
> then make it do all query/answer sequence by calling a C routine. Is there a  
> easy way out?  
> Can’t we make a C routine call a specific method in a Ruby Script.
> 
> Can we access a C stack from Ruby or vice versa while debugging the Ruby  
> extension.

There’s some discussion of this on pp 302-303 of the 2nd ed. of the  
Pickaxe.

The basic idea is to do the following in your C code.

1. include “ruby.h”

2. initialize ruby with:  
ruby\_init()  
ruby\_init\_load\_path()  
ruby\_script(“embedded”)  
This last sets up the name of a pseudo script file (and $0), and can  
be whatever you want.

3. include whatever ruby code you need with rb\_require, and/or  
rb\_load\_file

4. do what you want using the Ruby C language API. If at this point  
you called ruby\_run() you would be handing control over to the ruby  
interpreter, which would never return. In your case you don’t want to  
do that.

5. before you exit your C program call rb\_finalize() to clean up the  
ruby runtime environment.

–  
Rick DeNatale

My blog on Ruby  
[http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)

IPMS/USA Region 12 Coordinator  
[http://ipmsr12.denhaven2.com/](http://ipmsr12.denhaven2.com/)

Visit the Project Mercury Wiki Site  
[http://www.mercuryspacecraft.com/](http://www.mercuryspacecraft.com/)

---

<div class="post-metadata">

**Author:** ![Saumya\_D](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/eada6e/32.png) [@Saumya\_D](https://www.ruby-forum.com/u/Saumya_D)\
**Post date:** [September 6, 2006, 8:10pm UTC](https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591/3 "2006-09-06T20:10:46Z")

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On 9/6/06, Saumya D. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> def bad  
> puts ‘I am bad’  
> end

> I want to include one of these methods from C code.  
> Since executing a script in this case will simply  
> Do nothing as I have defined singletons here.  
> How do I acheve It.

I beleive that this will work, none of this actually tested.

First, they’re not singleton methods, methods defined at the top level  
are private instance methods of class Object. So you need to have a  
receiver, but any object will do, say nil. As far as I can tell the  
rb\_funcall function doesn’t check whether or not a method is private,  
but this might change in future versions of ruby.

So something like this might work to call the good method.

```
 rb_funcall(Qnil, rb_intern("good"), 0)

```

if you instead made these class methods of a class:

class TestClass  
def TestClass.good  
puts ‘I am gud’  
end

```
 def TestClass.bad
       puts 'I am bad'
 end

```

end

Then in your C code you could do something like this (again untested):

```
 VALUE test_class = rb_const_get(rb_cObject, 

```

rb\_intern(“TestClass”));  
rb\_funcall(test\_class, rb\_intern(“good”), 0, 0)

The last two arguments to rb\_funcall are the number of arguments and  
an array of the VALUEs of the arguments, since the count is 0 we can  
use 0 for the array.

And if you made the methods instance methods:

class TestClass  
def good  
puts ‘I am gud’  
end

```
 def bad
       puts 'I am bad'
 end

```

end

Then your C code might look something like this (once again untested):

```
 VALUE test_class = rb_const_get(rb_cObject, 

```

rb\_intern(“TestClass”));  
VALUE test\_instance = rb\_class\_new\_instance(0,0,test\_class)  
rb\_funcall(test\_instance, rb\_intern(“good”), 0, 0)

similarly here, the first two arguments of rb\_class\_new\_instance are  
the argument count and argument array for the initialize method.

–  
Rick DeNatale

My blog on Ruby  
[http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)

---

<div class="post-metadata">

**Author:** ![Saumya\_D](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/eada6e/32.png) [@Saumya\_D](https://www.ruby-forum.com/u/Saumya_D)\
**Post date:** [September 8, 2006, 8:25am UTC](https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591/4 "2006-09-08T08:25:05Z")

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Thanks a bundle.  
Tested Successfully.

Saumya.

---

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**Author:** ![Saumya\_D](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/eada6e/32.png) [@Saumya\_D](https://www.ruby-forum.com/u/Saumya_D)\
**Post date:** [September 6, 2006, 10:41am UTC](https://www.ruby-forum.com/t/calling-method-defined-in-ruby-script-from-external-world/67591/5 "2006-09-06T10:41:33Z")

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Just to clarify, “rb\_load\_file” and “ruby\_run” will execute the ruby  
script.  
But incase, there are more than one singleon methods defined in the  
script  
and I want to call only one of them.

If I have a “test.rb”

def good  
puts ‘I am gud’  
end

def bad  
puts ‘I am bad’  
end

I want to include one of these methods from C code.  
Since executing a script in this case will simply  
Do nothing as I have defined singletons here.  
How do I acheve It.

Saumya.