About

Method Lister is used to query objects and discover which ancestor implements
which methods. It’s quite common to have a lot of mixins and several classes
in an object’s class hierarchy, especially in a Rails application. To help
with this Method Lister adds the ability to find out in which classes/modules
the methods on an object are implemented.

Method Lister adds 3 methods to all objects in the system: ls, grep, and
which. Since these names are sometimes taken you can also use mls,
mgrep, and mwhich.

Method Lister is intended to be used from IRB or during debugging.

Install

Get the gem:

# Add GitHub as a Gem Source (only have to do this once)
gem sources -a http://gems.github.com

# Install the gem
sudo gem install matthew-method_lister

# Otherwise, build the gem and install it
rake gem
sudo gem install pkg/*.gem

Open up ~/.irbrc and add these lines:

require 'rubygems'
require 'method_lister'

Usage

ls or mls

The ls command will list all methods an object responds to, organized by the
module or class which provides the implementation. For example (results may
vary, depending on what you have loaded):

>> [].ls
========== Module Kernel ==========
PUBLIC: == === =~ __id__ __send__ class clone display dup eql? equal?
extend freeze frozen? gem grep hash id inspect instance_eval instance_of?
instance_variable_defined? instance_variable_get instance_variable_set
instance_variables is_a? kind_of? ls method methods mgrep mls mwhich nil?
object_id pretty_inspect private_methods protected_methods public_methods
require respond_to? send singleton_methods taint tainted? to_a to_s type
untaint which

PRIVATE: Array Float Integer String URI ` abort at_exit autoload autoload?
binding block_given? callcc caller catch chomp chomp! chop chop! eval exec
exit exit! fail fork format gem_original_require getc gets
global_variables gsub gsub! initialize_copy iterator? lambda load
local_variables loop method_missing open p pp print printf proc putc puts
raise rand readline readlines remove_instance_variable scan select
set_trace_func singleton_method_added singleton_method_removed
singleton_method_undefined sleep split sprintf srand sub sub! syscall
system test throw trace_var trap untrace_var warn

========== Module PP::ObjectMixin ==========
PUBLIC: pretty_print pretty_print_cycle pretty_print_inspect
pretty_print_instance_variables

========== Class Object ==========
PRIVATE: initialize irb_binding timeout

========== Module Enumerable ==========
PUBLIC: all? any? collect detect each_with_index entries find find_all
grep include? inject map max member? min partition reject select sort
sort_by to_a zip

========== Class Array ==========
PUBLIC: & * + - << <=> == [] []= assoc at clear collect collect! compact
compact! concat delete delete_at delete_if each each_index empty? eql?
fetch fill first flatten flatten! frozen? hash include? index indexes
indices insert inspect join last length map map! nitems pack pop
pretty_print pretty_print_cycle push rassoc reject reject! replace reverse
reverse! reverse_each rindex select shift size slice slice! sort sort!
to_a to_ary to_s transpose uniq uniq! unshift values_at zip |

PRIVATE: initialize initialize_copy

You can show only the public methods by passing in “true”:

>> [].ls true
========== Module Kernel ==========
PUBLIC: == === =~ __id__ __send__ class clone display dup eql? equal?
extend freeze frozen? gem grep hash id inspect instance_eval instance_of?
instance_variable_defined? instance_variable_get instance_variable_set
instance_variables is_a? kind_of? ls method methods mgrep mls mwhich nil?
object_id pretty_inspect private_methods protected_methods public_methods
require respond_to? send singleton_methods taint tainted? to_a to_s type
untaint which

========== Module PP::ObjectMixin ==========
PUBLIC: pretty_print pretty_print_cycle pretty_print_inspect
pretty_print_instance_variables

========== Module Enumerable ==========
PUBLIC: all? any? collect detect each_with_index entries find find_all
grep include? inject map max member? min partition reject select sort
sort_by to_a zip

========== Class Array ==========
PUBLIC: & * + - << <=> == [] []= assoc at clear collect collect! compact
compact! concat delete delete_at delete_if each each_index empty? eql?
fetch fill first flatten flatten! frozen? hash include? index indexes
indices insert inspect join last length map map! nitems pack pop
pretty_print pretty_print_cycle push rassoc reject reject! replace reverse
reverse! reverse_each rindex select shift size slice slice! sort sort!
to_a to_ary to_s transpose uniq uniq! unshift values_at zip |

grep or mgrep

The grep command takes a regular expression and only returns methods which
match the given regex. In this example we’ll use mgrep since on Array
objects grep is already taken:

>> [].mgrep /f/
========== Module Kernel ==========
PUBLIC: freeze frozen? instance_of? instance_variable_defined? kind_of?

PRIVATE: fail fork format method_missing printf set_trace_func
singleton_method_undefined sprintf

========== Module Enumerable ==========
PUBLIC: find find_all

========== Class Array ==========
PUBLIC: delete_if fetch fill first flatten flatten! frozen? shift unshift

Similar to ls you can pass in an extra argument of “true” to see only the
public methods:

>> [].mgrep /f/, true
========== Module Kernel ==========
PUBLIC: freeze frozen? instance_of? instance_variable_defined? kind_of?

========== Module Enumerable ==========
PUBLIC: find find_all

========== Class Array ==========
PUBLIC: delete_if fetch fill first flatten flatten! frozen? shift unshift

Note that method_missing is always considered a match, since it could always
potentially execute.

which or mwhich

The which command is for finding which classes or modules implement the
method you’re seeking. You can pass the method name in as a string or symbol.

>> [].which :to_a
========== Module Kernel ==========
PUBLIC: to_a

========== Module Enumerable ==========
PUBLIC: to_a

========== Class Array ==========
PUBLIC: to_a

Logically the which command is the same as grep(/^your_method$/) and so
the same comments apply about method_missing and the optional parameter to
see only public methods.

Known Bugs

If a singleton method overrides some method from an ancestor then the method
will be reported on the ancestor only and not both the ancestor and the
eigenclass. For example:

>> class Foo; def doit; end; end
=> nil

>> f = Foo.new
=> #<Foo:0x3395a0>

>> class << f; def doit; end; end
=> nil

>> f.mgrep /doit/
========== Module Kernel ==========
PRIVATE: method_missing

========== Class Foo ==========
PUBLIC: doit

This was done on purpose to support listing singleton methods on cloned
objects. I couldn’t support both features since the reflection methods for
eigenclasses are buggy.

License

Copyright 2008, 2009, Matthew O’Connor All rights reserved.

This program is free software; you can redistribute it and/or modify it under
the same terms as Ruby 1.8.7 itself.