# How can we create instance method and class methods at runtime in ruby? **URL:** \ **Category:** ruby-talk\ **Created:** [23 July 2013 04:43 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231 "2013-07-23T04:43:41Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [23 July 2013 04:43 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231/1 "2013-07-23T04:43:41Z")
How can we create instance method and class methods at runtime in ruby? class Foo   def test     p "hi"   end end foo = Foo.new foo.test # =\> "hi" class Foo   def test     p "hiyy"   end end foo.test # \>\> "hi" # \>\> "hiyy" How Can I re-define the `test` method at runtime? I tried `define_method`,but it didn't work for this. > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Tamara\_Temple1](https://avatars.discourse-cdn.com/v4/letter/t/5f9b8f/32.png) [@Tamara\_Temple1](https://rubytalk.org/u/Tamara_Temple1)\ **Post date:** [23 July 2013 05:23 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231/2 "2013-07-23T05:23:10Z")
Don't know what you're doing, but this works: $ irb 2.0.0p247 :001 \> class Foo; def test; p "hi"; end;end =\> nil 2.0.0p247 :002 \> foo = Foo.new =\> #\ 2.0.0p247 :003 \> foo.test "hi" =\> "hi" 2.0.0p247 :004 \> class Foo; def test; p "bye"; end;end =\> nil 2.0.0p247 :005 \> foo.test "bye" =\> "bye" 2.0.0p247 :006 \> class Foo; def self.test; p "bazinga!"; end;end =\> nil 2.0.0p247 :007 \> Foo.test "bazinga!" =\> "bazinga!" 2.0.0p247 :008 \> foo.test "bye" =\> "bye" > **···** > > On Jul 22, 2013, at 11:43 PM, Love U Ruby \ wrote: > > > How can we create instance method and class methods at runtime in ruby? > > > > class Foo > > def test > >    p "hi" > > end > > end > > foo = Foo.new > > foo.test # =\> "hi" > > class Foo > > def test > >    p "hiyy" > > end > > end > > foo.test > > # \>\> "hi" > > # \>\> "hiyy" > > > > How Can I re-define the `test` method at runtime? I tried > > `define_method`,but it didn't work for this. > > > > -- > > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [23 July 2013 06:51 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231/3 "2013-07-23T06:51:18Z")
Sorry for creating the confusions:- Here I tried once more to explain what I was looking for: class Foo   def test     p "hi"   end end foo = Foo.new foo.test # =\> "hi" Foo.define\_method(:test){p "hello"} # private method `define\_method' called for Foo:Class (NoMethodError) Any method is there to re-define the method `test` without re-opening the class in runtime? Thanks > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Stefano\_Crocco](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@Stefano\_Crocco](https://rubytalk.org/u/Stefano_Crocco)\ **Post date:** [23 July 2013 07:01 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231/4 "2013-07-23T07:01:04Z")
You can use class\_eval: Foo.class\_eval do   define\_method(:test){p 'hello'} end or you can use send: Foo.send :define\_method, :test, &proc{p 'hello'} I hope this helps Stefano > **···** > > On Tuesday 23 July 2013 Love U Ruby wrote > > > Sorry for creating the confusions:- > > > > Here I tried once more to explain what I was looking for: > > > > class Foo > >   def test > >     p "hi" > >   end > > end > > foo = Foo.new > > foo.test # =\> "hi" > > Foo.define\_method(:test){p "hello"} > > # private method `define\_method' called for Foo:Class (NoMethodError) > > > > Any method is there to re-define the method `test` without re-opening > > the class in runtime? > > > > Thanks > > > > -- > > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [23 July 2013 11:18 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231/5 "2013-07-23T11:18:31Z")
Stefano Crocco wrote in post #1116318: > **···** > > > On Tuesday 23 July 2013 Love U Ruby wrote > > > > Foo.class\_eval do > >   define\_method(:test){p 'hello'} > > end > > > > or you can use send: > > > > Foo.send :define\_method, :test, &proc{p 'hello'} > > > > I hope this helps > > > > Stefano > > Thanks @Stefano - this is what I was looking for.. 🙂 > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Tamara\_Temple1](https://avatars.discourse-cdn.com/v4/letter/t/5f9b8f/32.png) [@Tamara\_Temple1](https://rubytalk.org/u/Tamara_Temple1)\ **Post date:** [23 July 2013 13:29 UTC](https://rubytalk.org/t/how-can-we-create-instance-method-and-class-methods-at-runtime-in-ruby/68231/6 "2013-07-23T13:29:41Z")
Be circumspect in doing this with define\_method. It's a lot slower when you call the method: > > **···** > > On Jul 23, 2013, at 6:18 AM, Love U Ruby \ wrote: > > > Stefano Crocco wrote in post #1116318: > > > > > On Tuesday 23 July 2013 Love U Ruby wrote > > > > > > Foo.class\_eval do > > > define\_method(:test){p 'hello'} > > > end > > > > > > or you can use send: > > > > > > Foo.send :define\_method, :test, &proc{p 'hello'} > > > > > > I hope this helps > > > > > > Stefano > > > > Thanks @Stefano - this is what I was looking for.. 🙂 > > > > -- > > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).