From: "Mauricio Fernández" <batsman.geo@...>
Date: 2003-03-31T20:14:14+09:00
Subject: Re: how to catch any exception "eval" throws

On Mon, Mar 31, 2003 at 03:13:15PM +0900, ahoward wrote:
> On Mon, 31 Mar 2003, Meinrad Recheis wrote:
> 
> > i tried
> >
> > begin
> > 	eval( str )
> > rescue
> > 	puts $!
> > end
> >
> > but my program terminates if str contains erraneous expressions
> > why doesn t rescue catch say "parser errors"?
> <snip>
> 
>   ~ > cat foo.rb
>   #!/usr/bin/env ruby
> 
>   %w[ error ;|;| raise('badthings') ].each do |badthing|
>     begin
>       eval badthing
>     rescue NameError, SyntaxError, StandardError => err

Exception should be enough unless somebody is knowingly raising other
things... (it's at the top of the exception class hierarchy)

[one minute later]

It's actually impossible to raise something unrelated to Exception:

>> class A; end
=> nil
>> raise A
TypeError: exception class/object expected
        from (irb):3:in `raise'
        from (irb):3
>> raise 1
TypeError: exception class/object expected
        from (irb):4:in `raise'
        from (irb):4
>> a = A.new
=> #<A:0x40207fbc>
>> class << a; def exception; A; end; end
=> nil
>> raise a
TypeError: exception object expected
        from (irb):10:in `raise'
        from (irb):10

begin
....
rescue Exception
...
end

will thus catch everything. 


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