simple dsl in ruby c api

just a simple dsl to accept a block on a module’s ‘run’ method and eval the contents in the context of the module.

#include <ruby.h>
#include <stdio.h>

VALUE jm_Module;

VALUE
m_run(VALUE self) {

  if (rb_block_given_p ()) {
     rb_mod_module_eval(0,0,self);
     return Qnil;

   }

   else

     rb_raise (rb_eRuntimeError, "must be called with a block");

     return Qnil;

}

VALUE
m_hello(VALUE self) {
  printf("hello world\n");

  return Qnil;
}

void
Init_blocks() {
   jm_Module = rb_define_module("Block");

  rb_define_module_function(jm_Module, "run", m_run, 0);

  rb_define_module_function(jm_Module, "hello", m_hello, 0);
}

equivalent ruby code would be:

module Block
  module_function

  def run(&b)
     module_eval(&b)
   end

  def hello
     puts "hello world"

  end

end

use like this:

Block.run { hello }

contents of block will be executed within context of the module, so can invoke module methods.

Tags: C, dsl, ruby