# Is there an easy way to extend an object? **URL:** \ **Category:** Ruby\ **Created:** [December 28, 2005, 2:40am UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209 "2005-12-28T02:40:04Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![jeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e19b73/32.png) [@jeff](https://www.ruby-forum.com/u/jeff)\ **Post date:** [December 28, 2005, 2:40am UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209/1 "2005-12-28T02:40:04Z")
Given an object, is there a clean way of creating a new object that wraps the original and then adds a new method? It doesn’t have to wrap the old object if there’s a way to directly add a new method to the object (I’m allowed to change the incoming object). def extend\_it(obj) # how do I add a method to obj # or create a wrapper for it? return obj #or new\_obj that quacks like obj, has obj data, and also has extra method end In my C++ days I would create a class that derives from the original class, extends it with a new method, and defines a copy constructor to copy the state of the original object. Thanks Jeff ---
**Author:** ![jeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e19b73/32.png) [@jeff](https://www.ruby-forum.com/u/jeff)\ **Post date:** [December 28, 2005, 2:47am UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209/2 "2005-12-28T02:47:16Z")
Hi – On Wed, 28 Dec 2005, Jeff C. wrote: > Given an object, is there a clean way of creating a new object that > wraps the original and then adds a new method? > > It doesn’t have to wrap the old object if there’s a way to directly add > a new method to the object (I’m allowed to change the incoming object). > > def extend\_it(obj) > > # how do I add a method to obj > > # or create a wrapper for it? You can directly define a method on a particular object: def obj.new\_method … end You can also create a module, and then use ‘extend’ to add that module’s instance method’s to the object’s capabilities. module M def x end end obj.extend(M) There are a few more variants on these if they’re not what you need… David – David A. Black removed\_email\_address@domain.invalid “Ruby for Rails”, from Manning Publications, coming April 2006! > **[Ruby for Rails](https://www.manning.com/books/ruby-for-rails)** > > NEWER EDITION AVAILABLE > > The Well-Grounded Rubyist, Second Edition is now available. An eBook of the previous edition, The Well-Grounded Rubyist is included at no additional cost when you buy the revised edition! > > > Ruby for Rails helps Rails... ---
**Author:** ![jeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e19b73/32.png) [@jeff](https://www.ruby-forum.com/u/jeff)\ **Post date:** [December 28, 2005, 2:55am UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209/3 "2005-12-28T02:55:50Z")
unknown wrote: > You can directly define a method on a particular object: > > def obj.new\_method > … > end That worked great! Thanks. Jeff ---
**Author:** ![jeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e19b73/32.png) [@jeff](https://www.ruby-forum.com/u/jeff)\ **Post date:** [December 28, 2005, 2:43pm UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209/4 "2005-12-28T14:43:23Z")
Jeff C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Jeff > Just for the sake of completeness: if you are not allowed to modify the > original instance or do not want to do it there’s a delegator module: > > require ‘delegate’ > > =\> true > > s=“foo” > > =\> “foo” > > o=SimpleDelegater.new s > > =\> “foo” > > o.length > > =\> 3 > > def o.foo() length \* 2 end > > =\> nil > > o.foo > > =\> 6 > > o \<\< “bar” > > =\> “foobar” > > o.length > > =\> 6 > > o.foo > > =\> 12 Kind regards ``` robert ``` ---
**Author:** ![jeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e19b73/32.png) [@jeff](https://www.ruby-forum.com/u/jeff)\ **Post date:** [December 28, 2005, 5:07pm UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209/5 "2005-12-28T17:07:08Z")
Robert K. wrote: > Just for the sake of completeness: if you are not allowed to modify the > original instance or do not want to do it there’s a delegator module: Now that is also really cool. Ruby is my first “dynamic” language and I’m starting to see how powerful it can be. Thanks for the tip. Jeff > **[Hey Daddio!](http://www.softiesonrails.com)** > > Home of Hey Daddio Software ---
**Author:** ![jeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e19b73/32.png) [@jeff](https://www.ruby-forum.com/u/jeff)\ **Post date:** [December 28, 2005, 8:18am UTC](https://www.ruby-forum.com/t/is-there-an-easy-way-to-extend-an-object/51209/6 "2005-12-28T08:18:04Z")
Jeff… In a more-or-less “pure” OO language like Ruby (or Smalltalk), you don’t have to go through all those gyrations that C++ (and other languages that added OO after the fact) forced us to use. You just add a method to the existing object because classes are first-class objects. Cool, eh? On Dec 27, 2005, at 5:40 PM, Jeff C. wrote: > # how do I add a method to obj > > Thanks > Jeff > > – > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. -.-.-.-.-.-.-.-.-.-.-.-.-.-.- Dan S. Technology Visionary - Technology Assessment - Documentation “Looking at technology from every angle” > **[Eclecticity.com is for sale | HugeDomains](https://www.hugedomains.com/domain_profile.cfm?d=eclecticity.com)** > > Shop a wide selection of domains at HugeDomains.com. Find the right domain name today.