From: centrepins@... (Glenn)
Date: 2005-02-15T15:14:53+09:00
Subject: Re: Where does this "global code" fit in?

Excellent Florian, many thanks!


Florian Gross <flgr@ccan.de> wrote in message news:<37cb91F5c4d56U1@individual.net>...
> Glenn wrote:
> 
> > class Window
> >   #some code here (assume a method "show" is defined somewhere)
> > end
> > 
> > w = Window.new    #<<<
> > w.show            #<<<
> > 
> > It's the two lines at the end that confuse me.  My natural though is
> > they are "global", but in a pure-OO world, they've got to fit into a
> > class somewhere?  If so, are they actually fitting into (extending)
> > class "Object" in some way?  Where?  How?
> 
> In the Java world they would have to go into a Class. But Ruby is 
> expression based and more rational -- if you type in code at the top 
> level it will be executed in the context of a special regular Object 
> which is called 'main'. It's just a regular Object with a few custom 
> methods that are just defined for that particular Object (singleton 
> methods) -- note that it's a regular Object meaning it has the methods 
> in the Kernel class available to it as well!
> 
> Note that even the definitions of classes and everything else are 
> executed in that context. Ruby is consistent.
> 
> Here's the list of special methods the top-level Object has:
> 
> > C:\dev.svn\ruby>ruby                                                           
> > puts methods(false).sort.map { |name| [name, method(name).inspect].join(": ") }
> > ^Z                                                                             
> > include: #<Method: main.include>                                               
> > private: #<Method: main.private>                                               
> > public: #<Method: main.public>                                                 
> > to_s: #<Method: main.to_s>                                                     
> 
> include is usually not defined for Objects, but only for Modules. 
> main.include is equivalent to doing Object.send(:include, ...).
> 
> private and public are usually only for Modules as well, but if you 
> define a method at the top level it is defined in Kernel. So it does 
> make sense to be able to overwrite the visibility of these as well. 
> Default visibility at the top level is private, for Modules it defaults 
> to public.
> 
> main.to_s just returns 'main'.
> 
> Hope this was of help.