From: Kevin Brown <blargity@...>
Date: 2005-09-28T15:52:54+09:00
Subject: Re: class variables

On Wednesday 28 September 2005 00:03, v.nainar wrote:
> Hello!
>
>  What is wrong with the following code? Why is  @@id  incremented before
> and not after the assignment? .  ( Sorry  if this sounds silly and I have
> overlooked something obvious )
>
>
> #!/usr/local/bin/ruby
> class Foo
>   @@id=1
>   def initialize(s)
>     @s=s
>     @id=setId()
>   end
>   def setId()
>     @id=@@id
>     @@id+=1
>   end
> end
>
> foo1=Foo.new("one")
> foo2=Foo.new("two")
> foo3=Foo.new("three")
> p foo1,foo2,foo3
> Output ->
> # <Foo:0xb7d6b4f0 @id=2, @s="one">   # why is @id not 1
> # <Foo:0xb7d6b4c8 @id=3, @s="two">   # and 2
> # <Foo:0xb7d6b4a0 @id=4, @s="three"> # and 3 ?

When somethings at the end of a function, it gets returned implicitly.  So, 
when you call @id - setId() you're setting @id to the current id (1), then 
incrementing, and then then function returns the incremented value, 
overwriting your 1 with a 2.  Throw a return @s at the end and you'll get the 
behaviour you're looking for.