I'm writing code that attempts to fetch a page from a web server, and
needs to be able to handle failures gracefully. Specifically, if the
URL in hand is bogus, I want to be able to log that fact, and not have
my script blow up.
Being used to "try" from other languages, I can do the following:
REBOL [ Author: "Joel Neely" ]
gotpage?: func [ pagename /local result ][
either error? try [read pagename]
[ print "Bletch!" return false ]
[ print "Hooray!" return true ]
]
which behaves as follows:
>> system/version
== 2.1.2.3.1
>> gotpage? http://www.fedex.com/
Hooray!
== true
>> gotpage? http://nohost.org/nopage.html
Bletch!
== false
Based on the REBOL Dictionary entries for try, error!, and error?, I
assumed that try would return a data value/object that I could use
subsequently. Thinking that I'd like to save the error message for
logging, I attempted the following technique:
REBOL [ Author: "Joel Neely" ]
gotpage?: func [ pagename /local result ][
result: try [read pagename]
either error? result
[ print "Bletch!" return false ]
[ print "Hooray!" return true ]
]
with the following results (lines wrapped to fit email)
>> gotpage? http://www.fedex.com/
Hooray!
== true
>> gotpage? http://nohost.org/nopage.html
** User Error: Error. Target url: http://nohost.org/nopage.html
could not be retrieved.
Server response: HTTP/1.0 503 Service Unavailable.
** Where: read pagename
>>
Can error values not be stored in a variable? How can I retain the
error message for future reference without my entire script crashing?
Thanks in advance for any hints!
-jn-
