From: Pit Capitain <pit@...>
Date: 2006-10-17T04:39:00+09:00
Subject: Re: include inside and outside classes

John Ky schrieb:
> Why is it that when I can do this:
> 
>> include Math
>> puts sqrt(169)
> 
> I can't do this?:
> 
>> class X
>>   include Math
>>   puts sqrt(169)
>> end

Rick has already written about the differences between class scope and 
toplevel scope. (Are you reading this, Tom?)

With #include you can call the Math methods in instance methods:

   class X
     include Math
     def m
       puts sqrt(169)
     end
   end

   X.new.m  # => 13.0

If you want to call the methods in class scope, you have to use #extend:

   class X
     extend Math
     puts sqrt(169)  # => 13.0
   end

Regards,
Pit