From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-02-19T02:41:53+09:00
Subject: Re: Method prototypes like C++? // Compiling executables

On Thu, Feb 18, 2010 at 6:28 PM, Claudio Freda <ferdil.kiwi@gmail.com> wrote:
> Rob Biedenharn wrote:
>> Sure just do it!  Methods only need to exist when then are "called"
>> and even then you can use the method_missing hook to define them on
>> the fly if you need to.
>
> Wait, I explain my problem.
> In C++ I would have been able to to this:
>
> void function();
> function();
> void function() {
>  cout<<"The function has been executed"
> }
>
> And it would still print "The function has been executed"
>
> In ruby instead if I do this:
>
> def method; end
>
> method
>
> def method
>  print ('The method has been executed')
> end
>
> it just prints me nothing; I think it has something to do with ruby's
> dynamic definitions.
>
> Just how to achieve the same thing in ruby? (summoning a function that
> is declared later in the code)

What Rob wanted to say is that you don't need to declare a function
(method). You just call it, and it has to have been defined before the
call. But be aware that the code inside a method is not executed when
it's parsed, only when the method is called, so you can have this:

irb(main):001:0> def caller
irb(main):002:1> method("a")
irb(main):003:1> end
=> nil
irb(main):004:0> def method(s)
irb(main):005:1> puts s
irb(main):006:1> end
=> nil
irb(main):007:0> caller
a

You can have the definition of caller before the definition of method.
What you can't do is call caller before defining method.

Hope this clears up a bit,

Jesus.