From: matz@... (Yukihiro Matsumoto)
Date: 2001-05-03T15:03:54+09:00
Subject: [ruby-talk:14582] Re: Arggg Bitten by the block var scope feature!!!

Hi,

In message "[ruby-talk:14557] Arggg Bitten by the block var scope feature!!!"
    on 01/05/03, Wayne Scott <wscott@bitmover.com> writes:

|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 problem can be avoided in the future version, using <> instead of ||.

							matz.