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comp.lang.ruby

problems with rescue clause.

Russell Fulton

1/18/2006 11:22:00 PM

Hi Folks,
I'm writing a script to check passwords against email accounts,
so I have written a method:

def tryIMAP (host, usessl, user, pass)

proto = usessl ? "IMAPS" : "IMAP"
begin
imap = Net::IMAP.new(host, usessl ? 993 : 143, usessl)
rescue SystemCallError
raise "#{proto} failed"
rescue SocketError
raise "#{proto} failed"
end
begin
imap.login( user, pass)
imap.logout
'success'
rescue Net::IMAP::NoResponseError
'failure'
end

end


I use the method like this...

while proto do
begin
case proto
when 'IMAPS'
status = tryIMAP(server, true, user, iD )

proto = nil
when 'IMAP'
status = tryIMAP(server, false, user, iD )
proto = nil
when 'POP'
status = tryPOP(server, user, iD )
proto = nil
else
proto = nil
end
rescue 'IMAPS failed'
proto = 'IMAP'
rescue 'IMAP failed'
proto = 'POP'
rescue 'POP failed'
servers[host][0] = 'NO'
proto = nil
STDERR.print "failed to connect to #{server}\n"
end
end # while proto
print "logged in for #{target}\n" if status == 'success'

If I try a server which does not support IMAPS I get:
class or module required for rescue clause (TypeError)

I'm at a loss to figure out what is wrong. I've googled on the error
message but have not found anything useful.

BTW I'm new to ruby and I'd welcome criticism of the above code. If
there are better ways of doing this I'd love to know.

Cheers, Russell

--
Posted via http://www.ruby-....
2 Answers

Wilson Bilkovich

1/18/2006 11:38:00 PM

0

I would recommend doing:
raise RuntimeError, "#{proto} failed"
..instead of:
raise "#{proto} failed"

Then you can do rescue RuntimeError => e
..and e.message will contain the text of the exception. (e.g. IMAP failed)

Also, you don't really need two identical rescue clauses at the top,
for the two different kinds of error.
Personally, I would prevent try_imap from ever raising an exception,
and just return a status code. One for success, one for failure, and
one for an exception. That would greatly clean up the code that calls
it.

On 1/18/06, Russell Fulton <r.fulton@auckland.ac.nz> wrote:
> Hi Folks,
> I'm writing a script to check passwords against email accounts,
> so I have written a method:
>
> def tryIMAP (host, usessl, user, pass)
>
> proto = usessl ? "IMAPS" : "IMAP"
> begin
> imap = Net::IMAP.new(host, usessl ? 993 : 143, usessl)
> rescue SystemCallError
> raise "#{proto} failed"
> rescue SocketError
> raise "#{proto} failed"
> end
> begin
> imap.login( user, pass)
> imap.logout
> 'success'
> rescue Net::IMAP::NoResponseError
> 'failure'
> end
>
> end
>
>
> I use the method like this...
>
> while proto do
> begin
> case proto
> when 'IMAPS'
> status = tryIMAP(server, true, user, iD )
>
> proto = nil
> when 'IMAP'
> status = tryIMAP(server, false, user, iD )
> proto = nil
> when 'POP'
> status = tryPOP(server, user, iD )
> proto = nil
> else
> proto = nil
> end
> rescue 'IMAPS failed'
> proto = 'IMAP'
> rescue 'IMAP failed'
> proto = 'POP'
> rescue 'POP failed'
> servers[host][0] = 'NO'
> proto = nil
> STDERR.print "failed to connect to #{server}\n"
> end
> end # while proto
> print "logged in for #{target}\n" if status == 'success'
>
> If I try a server which does not support IMAPS I get:
> class or module required for rescue clause (TypeError)
>
> I'm at a loss to figure out what is wrong. I've googled on the error
> message but have not found anything useful.
>
> BTW I'm new to ruby and I'd welcome criticism of the above code. If
> there are better ways of doing this I'd love to know.
>
> Cheers, Russell
>
> --
> Posted via http://www.ruby-....
>
>

Russell Fulton

1/19/2006 12:12:00 AM

0

Thanks Wilson!

Wilson Bilkovich wrote:
> I would recommend doing:
> raise RuntimeError, "#{proto} failed"
> ..instead of:
> raise "#{proto} failed"
>
> Then you can do rescue RuntimeError => e
> ..and e.message will contain the text of the exception. (e.g. IMAP
> failed)

I'll give it a try.
>
> Also, you don't really need two identical rescue clauses at the top,
> for the two different kinds of error.

Hmmm.... I initially had the two errors on the same rescue but I got
syntax errors

> Personally, I would prevent try_imap from ever raising an exception,
> and just return a status code. One for success, one for failure, and
> one for an exception. That would greatly clean up the code that calls
> it.

Yep, that probably would be a better way of doing it but I wanted to
play with the exceptions:) It is one feature of ruby that I am not
familiar with from the other languages that I've used.

I'll probabaly cut it out of the final version.


--
Posted via http://www.ruby-....