# Ruby bug?

**URL:** <https://rubytalk.org/t/ruby-bug/12372>\
**Category:** ruby-talk\
**Created:** [1 July 2004 22:17 UTC](https://rubytalk.org/t/ruby-bug/12372 "2004-07-01T22:17:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Marek\_Janukowicz](https://avatars.discourse-cdn.com/v4/letter/m/b2d939/32.png) [@Marek\_Janukowicz](https://rubytalk.org/u/Marek_Janukowicz)\
**Post date:** [1 July 2004 22:17 UTC](https://rubytalk.org/t/ruby-bug/12372/1 "2004-07-01T22:17:48Z")

</div>

It is not. You cannot "redefine" class in Ruby - if you open the class again (as  
in bug2.rb file) and define some methods in it, they will be \_added\_ to the  
existing class.

> **···**
>
> On Wed, 30 Jun 2004 17:00:04 -0500, DaZoner wrote:
> 
> > Imagine you want to redefine a class at runtime. One way to do it is to load  
> > a different class definition at runtime.
> > 
> > So make two class definitions in separate files and a test script:
> > 
> > bug1.rb --------------------------------------------------------------------  
> > ----------
> > 
> > class Bug  
> > &nbsp;&nbsp;def method1  
> > &nbsp;&nbsp;end  
> > end
> > 
> > bug2.rb --------------------------------------------------------------------  
> > ----------
> > 
> > class Bug  
> > &nbsp;&nbsp;def method2  
> > &nbsp;&nbsp;end  
> > end
> > 
> > bugtest.rb -----------------------------------------------------------------  
> > ------------
> > 
> > load "bug1.rb"
> > 
> > b = Bug.new  
> > list = b.methods  
> > list.each { |methodName| print " ",methodName }  
> > print "\n"
> > 
> > load "bug2.rb"
> > 
> > b = Bug.new  
> > list = b.methods  
> > list.each { |methodName| print " ",methodName }  
> > print "\n"
> > 
> > ----------------------------------------------------------------------------  
> > --
> > 
> > Using Ruby 1.8.1 the second printed line shows Bug to respond to both  
> > method1 and method2 even though bug2.rb does not define method1. Is this a  
> > bug?
> 
> --  
> Marek Janukowicz

---

<div class="post-metadata">

**Author:** ![Jeff\_Mitchell](https://avatars.discourse-cdn.com/v4/letter/j/e480ec/32.png) [@Jeff\_Mitchell](https://rubytalk.org/u/Jeff_Mitchell)\
**Post date:** [1 July 2004 22:36 UTC](https://rubytalk.org/t/ruby-bug/12372/2 "2004-07-01T22:36:28Z")

</div>

There is no formal way to redefine a class, but you can do this,

irb(main):001:0\> class A ; end  
=\> nil  
irb(main):002:0\> Object.send(:remove\_const, :A)  
=\> A  
irb(main):003:0\> A.new  
NameError: uninitialized constant A  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;from (irb):3

> **···**
>
> --- Marek Janukowicz \<childNOSPAM@t17.ds.pwr.wroc.pl\> wrote:
> 
> > \>  
> > \> Using Ruby 1.8.1 the second printed line shows Bug to respond to both  
> > \> method1 and method2 even though bug2.rb does not define method1. Is this a  
> > \> bug?
> > 
> > It is not. You cannot "redefine" class in Ruby - if you open the class again (as  
> > in bug2.rb file) and define some methods in it, they will be \_added\_ to the  
> > existing class.
> 
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