# About class in module

**URL:** <https://www.ruby-forum.com/t/about-class-in-module/144402>\
**Category:** Ruby\
**Created:** [July 29, 2008, 12:36pm UTC](https://www.ruby-forum.com/t/about-class-in-module/144402 "2008-07-29T12:36:37Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [July 29, 2008, 12:36pm UTC](https://www.ruby-forum.com/t/about-class-in-module/144402/1 "2008-07-29T12:36:37Z")

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– test1.rb –

class C  
def a  
end  
end

class C  
def a  
puts “override”  
end  
end

puts C.new.a # =\> override

– test2.rb –

class C  
def a  
end  
end

module M  
class C  
def a  
puts “why not override?”  
end  
end  
end

include M

puts C.new.a # =\> nil

########################

# Help Me^^

########################

---

<div class="post-metadata">

**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [July 29, 2008, 12:42pm UTC](https://www.ruby-forum.com/t/about-class-in-module/144402/2 "2008-07-29T12:42:16Z")

</div>

On Tuesday 29 July 2008, Kyung won Cheon wrote:

> end
> 
> puts C.new.a # =\> nil
> 
> ########################
> 
> # Help Me^^
> 
> ########################

C and C::M are two different classes. Modules work as namespaces, so  
that you  
can have different classes with the same name, provided they’re in  
different  
modules.

Stefano

---

<div class="post-metadata">

**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [July 29, 2008, 2:59pm UTC](https://www.ruby-forum.com/t/about-class-in-module/144402/3 "2008-07-29T14:59:28Z")

</div>

On 29.07.2008, at 12:41, Stefano C. wrote:

> C and C::M are two different classes

You mean M::C.

just my 2cents, Sandor  
Szücs

---

<div class="post-metadata">

**Author:** ![Kyung\_won\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/47e85d/32.png) [@Kyung\_won\_C](https://www.ruby-forum.com/u/Kyung_won_C)\
**Post date:** [July 29, 2008, 5:51pm UTC](https://www.ruby-forum.com/t/about-class-in-module/144402/4 "2008-07-29T17:51:51Z")

</div>

Kyung won Cheon wrote:

> end
> 
> puts C.new.a # =\> nil
> 
> ########################
> 
> # Help Me^^
> 
> ########################

Hhmm, this is actually a little tricky. If I had to hazard a guess I  
would say it’s related to the fact that modules included in X are higher  
in the lookup chain than X itself. e.g.:

module M  
def foo; “M-foo” end  
def foo2; “M-foo2” end  
end  
class A  
def foo; “A-foo” end  
include M  
end  
A.new.foo #=\> “A-foo”  
A.new.foo2 #=\> “M-foo2”

so I imagine the same rule applies to constant lookups:

module N  
BAR = “N-bar”  
BAR2 = “N-bar2”  
end  
class B  
BAR = “B-bar”  
include N  
end  
B::BAR #=\> “B-bar”  
B::BAR2 #=\> “N-bar2”

With warnings enabled, you would have seen that your test1.rb outputs:  
(irb):8: warning: method redefined; discarding old a