Sometimes you may be able to correct the cause of an exception. In
those cases, you can use the
retry statement within a
rescue
clause to repeat the entire
begin/
end block.
Clearly there
is tremendous scope for infinite loops here, so this is a feature to
use with caution (and with a finger resting lightly on the interrupt
key).
As an example of code that retries on exceptions, have a look at the
following, adapted from Minero Aoki's
net/smtp.rb library.
@esmtp = true
begin
# First try an extended login. If it fails because the
# server doesn't support it, fall back to a normal login
if @esmtp then
@command.ehlo(helodom)
else
@command.helo(helodom)
end
rescue ProtocolError
if @esmtp then
@esmtp = false
retry
else
raise
end
end
|
This code tries first to connect to an SMTP server using the
EHLO
command, which is not universally supported. If the connection attempt
fails, the code sets the
@esmtp variable to
false and
retries the connection. If this fails again, the exception is reraised
up to the caller.
