From: Daniel Brumbaugh Keeney <devi.webmaster@...>
Date: 2008-06-26T07:07:34+09:00
Subject: Re: puts a . which method of array is called

On Wed, Jun 25, 2008 at 1:50 PM, Raj Singh <neeraj.jsr@gmail.com> wrote:
> a = w(1 2 3)
>
> puts a

> I implemented
> class  Array
>  def to_s
>    'to_s is called'
>   end
>  def to_str
>    'to_str is called'
>  end
> end

I'm afraid you're barking up the wrong tree. In the IO#puts documentation,
" If called with an array argument, writes each element on a new line."
It could look something like this:
def puts(*objects)
  objects.each do |obj|
    if obj.kind_of? Array
      puts(*obj)
    else
      write(obj.to_s + $/
    end
  end
end

> Also I would like to know how to go about finding which method is called
> without looking at the c file. Is there some kind of trace I can do to
> detect which method was called?

ruby includes a library named tracer.
http://unroller.rubyforge.org/
Or you can write one yourself; Kernel#set_trace_func is really what a
tracing library reduces to.

Daniel Brumbaugh Keeney

I have provided my own home-grown tracer below, which, I'm afraid,
isn't much to speak of.

README

Quartzhouse is a tool for tracing Ruby programs so you can more quickly
familiarize yourself with the program flow. It's output is simple,
merely a long list of lines looking something like this:
RubyLex.lex_int2 at /usr/lib/ruby/1.8/irb/ruby-lex.rb:533

In fact, that's most all there is to QuartzHouse. Frankly, QuartzHouse
is really just Kernel.set_trace_func all spiffed up. It has nice
feature where you can call QuartzHouse.set_ignorables and any modules
already loaded will be ignored, but is otherwised unadorned.

PLEASE NOTE:

You should almost always redirect the output of QuartzHouse. By
default, it sends output to $stderr. Any reasonably complicated
program will have hundreds of lines of output.

EXAMPLES:

If I wanted to trace irb, I would do it like this:

ruby -wrquartzhouse -e'QuartzHouse.set_ignorables;require "irb";
QuartzHouse.start_trace;IRB.start' 2>irb_trace

This traces the runtime method calls of IRB (only those caused by the
IRB.start). It then redirects the output into a file `irb_trace', since
the default output is to $stderr. This can be changed by
Quartzhouse.output = IO_LIKE_OBJ
where IO_LIKE_OBJ can be anything that responds to `write'. Addional
filters can be placed by Quartzhouse.ignorables << a_module

I often filter output like this:
ruby -wrquartzhouse ... 2>1 1>/dev/null | grep something | uniq

#!/usr/bin/env ruby
# Author::    Daniel Brumbaugh Keeney (http://rubyforge.org/users/db-keen)
# Copyright:: 2008 Daniel Brumbaugh Keeney
# License::   GPLv3+
#
# This file is part of QuartzHouse.
#
# QuartzHouse is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# QuartzHouse is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with QuartzHouse.  If not, see <http://www.gnu.org/licenses/>.

require 'tempfile'
require 'cattr'

TOPLEVEL_OBJECT = self

module QuartzHouse

  TRACKING_PROC = proc do |event, file, line, id, binding, klass|

    if event=="call" or event=="c-call" or
      event==:call or event==:"c-call"

      unless @@ignorables.include? klass

        @@storage.puts "#{klass}.#{id} at #{file}:#{line}"

      end
    end
  end

  # Remove any ignored modules, delete any recorded trace, and set
  # output to $stderr.
  def QuartzHouse.reset
    @@storage.close(true) rescue false
    @@ignorables = Array.new
    @@output = $stderr
    @@storage = Tempfile.new "quartzhouse_tmp"
    nil
  end

  # Look through the ObjectSpace for any modules and adds them all to
  # the ignore list
  def QuartzHouse.set_ignorables
    ObjectSpace.each_object(Module) do |obj|
      @@ignorables << obj
    end
    @@ignorables << ENV << ARGV << ARGF << TOPLEVEL_OBJECT
  end

  # Use io.write to output the full trace record and close trace file.
  def QuartzHouse.print_trace io = @@output
    @@storage.close
    @@storage.open
    while line = @@storage.gets
      io.write line
    end
    @@storage.close
    nil
  end

  # Begin tracing, ignoring all the ignorables.
  def QuartzHouse.start_trace
    at_exit do
      set_trace_func nil
      print_trace $stderr
    end
    set_trace_func TRACKING_PROC
    nil
  end

  cattr_accessor :output, :ignorables

  QuartzHouse.reset

end