Problems with rescue clause


#1

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


#2

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.


#3

Thanks Wilson!

Wilson B. 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.