From: Chris Moline <ugly-daemon@...>
Date: 2001-05-03T10:46:03+09:00
Subject: [ruby-talk:14567] Re: Arggg Bitten by the block var scope feature!!!

On Thu, May 03, 2001 at 08:26:06AM +0900, Wayne Scott wrote:
> 
> I just spend a day debugging a elegant script that had this
> function.
> 
>     #simplified for this discussion
>     def fetch(arg2)
>         # cheesy block to flush cache if it has gotten too big
>      	if @cache.length > 200
>   	    # one pass at flushing cache
> 	    @cache.dup.each do |arg2, file|       ## (1)
>     		file.flush
>     		@cache.delete arg2
>     	    end
>     	end
> 	unless @cache[arg2]			  ## (2)
> 	    @cache[arg2] = @cl.new(@arg1, arg2)
> 	end
> 	@cache[arg2]
>    end
> 
> The bug is that at (1) the variable 'arg2' is not local to the block
> like I was expecting, but was just a copy of the function parameter
> 'arg2'.  So when I hit the normal part of the function at (2) the
> parameter is trashed if I happened to have executed (1).
> 
> This is a bad feature in a language that I am otherwise falling in
> love with.
I don't think its really a bad feature( actually I like it cause it comes in handy sometimes. ) I think that you just have to learn that preexisting variables show up in the block.

Sincerly,
Chris Moline