From: Peter Zotov <whitequark@...>
Date: 2012-05-28T20:56:31+09:00
Subject: Re: Garbage Collector(GC) and nil

Damián M. González писал 27.05.2012 18:10:
> Hello fellows, I'm wondering if I should set to nil any variables 
> that I
> will not use anymore for the sake of save memory system, I didn't see
> this way of work but I'm curious of what you can say.
>  I'm not sure about how GC works, tell me if I'm wrong: the GC will
> erase in memory those "labels" that are pointing to nil, so, if I set 
> to
> nil any variables, that space in memory will be free again.
>  I'll aprreciate any explanation.

Ruby MRI (other implementations work in a somewhat similar way) uses
mark-and-sweep garbage collector. When there is not enough memory, Ruby
"marks" all objects in the global scope, i.e. global variables, 
constant
contents and toplevel objects. Then it iterates through all marked 
objects
and marks all objects the marked objects refer to. Ruby continues this
cycle until no more objects are marked. Then it deallocates each 
non-marked
object, because if there's no references to an object, there is no way
to access it and it's not worth keeping.

Long story short, when you set a reference (e.g. an instance variable) 
to
nil, you remove a reference to whatever was stored there. If there are 
no
other references, the object will be destroyed.

-- 
   WBR, Peter Zotov.