From: Robert McGovern <tarasis@...>
Date: 2002-09-19T03:50:02+09:00
Subject: How best to use exceptions?

Hi, I am currently writting a module for reading id3 v1, v1.1 & v2.x 
tags. I figured the best way to learn was to rubyfying a playlist 
generator I'd previously written in java.

I have a method for reading the tag data from the file. At present I am 
asserting that certain conditions must exist i.e. the file must exist & 
that the file is readable. (slightly reformated for posting)

def readTag(filename)
     raise ArgumentError, "File does not exist" \
	unless FileTest.exist? filename
     raise IOError, "File is not readable" \
	unless FileTest.readable? filename

	<remainder ommited>
end

As the developer I know I can stipulate that this is how the module 
should be used. A contract, as such, that says give me a real readable 
file and I'll get the tag data.

However is this the right / best / most sensible way to go about it?

Rob