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Easy way to list public methods for a Ruby object

Submitted by alex on Thu, 03/26/2009 - 03:01.

I often have new code I'm trying to figure out, and constantly jumping back and forth between a console and a web browser with documentation sometimes really slows me down. Often times it's easy enough to remember which method you want just by seeing a list, even without detailed descriptions.

Any object has a public_methods method, which returns an array of strings listing the commands. Trouble is, all the methods it inherits are of course listed in there, and Object provides a LOT of stuff. It's easy for the interesting stuff about the instance at hand to get lost in that noise.

So, I'm trying a little experiment. I added this snippet to my ~/.irbrc file. Works on Linux and OSX, and in either normal irb or in the Rails console.

class Object
  # print public methods which are not inherited from Object
  def pm
    (self.public_methods - Object.public_methods).sort
  end
end
Now any object has a pm method. So what?

Loading development environment (Rails 2.2.2)
>> class Blah
>>   def foo; end
>>   def bar; end
>>   def blatz; end
>> end
=> nil
>> b = Blah.new
=> #<Blah:0x12b6b04>
>> b.pm
=> ["bar", "blatz", "foo"]
>> b.public_methods
=> ["returning", "to_yaml", "pretty_print_cycle", "inspect", "method_exists?", "stubs", "to_param", "extend_with_included_modules_from", "subclasses_of", "require_or_load", "clone", "method", "to_enum", "to_yaml_properties", "public_methods", "__metaclass__", "to_json", "suppress", "instance_variable_defined?", "instance_variable_names", "dclone", "equal?", "blatz", "freeze", "expects", "with_options", "foo", "methods", "respond_to?", "geometry_data_types", "instance_exec", "enable_warnings", "to_matcher", "to_query", "silence_warnings", "reset_mocha", "to_c", "dup", "enum_for", "instance_variables", "__id__", "copy_instance_variables_from", "duplicable?", "eql?", "object_id", "pretty_inspect", "require", "id", "send", "singleton_methods", "silence_stderr", "encode64", "class_eval", "taint", "taguri", "require_association", "stubba_method", "instance_variable_get", "frozen?", "instance_of?", "__send__", "require_library_or_gem", "b64encode", "to_a", "pretty_print", "taguri=", "daemonize", "remove_subclasses_of", "`", "type", "debugger", "blank?", "instance_eval", "protected_methods", "display", "==", "silence_stream", "unloadable", "decode64", "===", "acts_like?", "pm", "c", "to_yaml_style", "instance_variable_set", "extend", "kind_of?", "to_s", "extended_by", "class", "hash", "breakpoint", "present?", "mocha", "private_methods", "=~", "tainted?", "decode_b", "mocha_inspect", "instance_values", "untaint", "nil?", "load_with_new_constant_marking", "__is_a__", "bar", "stubba_object", "pretty_print_inspect", "require_dependency", "is_a?", "pretty_print_instance_variables", "metaclass"]

See the difference? Call it micro-documentation.

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