Building your Ruby environment and accessing it.

Building your Ruby environment

You can create classes both from C and Ruby together. Define the class in Ruby code just as a regular Ruby class, and then add C-code the manipulate the class definition.

Access Ruby from C

Lets first define some class in Ruby code, and try to access this from C:

Create a file wiki-example.rb with the following content:

module WikiExample
	class WikiManager
		attr_accessor :active
		def connect
			self.active = _we_connected
		end

		def get_version
			return 2
		end

		# _we_connected() is defined in C
	end
end

Then we write a C stub and small program to access this code. We first initialize mruby, then load the code file and the third step is to access the module, class and instance method.

Name the file wiki-example.c.

#include "mruby.h"
#include "mruby/irep.h"

int
main(void)
{
	mrb_state *mrb = mrb_open();
	if (!mrb) { /* handle error */ }
	FILE *fp = fopen("wiki-example.rb","r");

	// Load the data from the .rb file into the Ruby environment
	mrb_value obj = mrb_load_file(mrb,fp);

	// close the file
	fclose(fp); 

	// First access the module
    struct RClass *module = mrb_module_get(mrb, "WikiExample");
    
    // Get the class that is defined in the WikiExample module
    struct RClass *class = mrb_class_get_under(mrb, module, "WikiManager");

    // Create a new instance of WikiManager, no arguments are needed (0, NULL)
    mrb_value c = mrb_obj_new(mrb, class, 0, NULL);

    // Call the get_version method on the instance.
	mrb_value res = mrb_funcall(mrb, c, "get_version", 0);

	// Convert the result (a fixed number wrapped in a mrb_value)
	printf("result: %i\n", mrb_fixnum(res));
	
	// If crashed, provide exception info
	if (mrb->exc) 
  	{
    	mrb_print_error(mrb);
  	}
  	// Close the Ruby environment
	mrb_close(mrb);
}

Compile this code with gcc -std=c99 -Iinclude wiki-example.c build/host/lib/libmruby.a -o wiki-example and then run wiki-example. The output is result: 2.

Calling C methods from Ruby

Coming soon...