From: Niklas Frykholm <niklas@...>
Date: 2001-10-23T19:12:30+09:00
Subject: [ruby-talk:23033] Re: Error in Programming Ruby and patch suggestion for ruby

On Tue, Oct 23, 2001 at 05:24:37PM +0900, ts wrote:
> N>     +    StringValue(argv[0]);
> N>     +    rb_iv_set(self, "mesg", argv[0]);
>  Seems for me similar to Exception#message, no ?
> 
>   http://ruby-talk.com/17066

Hmmm... looking at this again I don't think RCR #22 (already
implemented) addresses the issue. And matz has rejected RCR #21...

If the problem is that the exceptions become mutable, it is OK for me
to first make a clone and then do rb_iv_set('mesg', argv[0]).

My concern is that I want to write an exception class which takes
something other than a message string in the initializer, but still
can be used with

    raise object, "message"

It seems to me that the semantics for raise should be that it should
take an exception object and a message. Not an exception and arguments
to its initializer... because that will only allow exceptions with
single argument initializers.

Today, I can only think of ugly solutions (the ones in my previous
message). Here is another ugly solution:

    class RetryError < StandardError
        attr_reader :ok
        def initialize(ok)
            if instance_variables.include?('@ok')
                super(ok)
            else
                @ok = ok
            end
        end
    end

And another:

    class RetryError < StandardError
        attr_reader :ok
        def initialize(ok, msg = "")
            super(msg)
            @ok = ok
        end
        def exception(*arg)
            if arg.size==0
                return self
            else
                return type.new(@ok, *arg)
            end
        end
    end

// Niklas