On 2/15/06, Michael Dinowitz <[EMAIL PROTECTED]> wrote:
> This is a question of best practices and why. When I know there's a chance of
> a specific error, I tend to code specifically to handle it. Others code
> generally using try/catch. Which is seen as best in other languages and why?
> I doubt there's any real performance issue between them, so it's a question
> of industry standard and style.
>
> For example, if I know an ID is needed on a page and it has to be a numeric
> I'd do:
> <CFIF Not IsDefined('ID')>
> An ID is needed
> <CFELSEIF Not IsNumeric(ID)>
> The passed ID needs to be numeric
> </CFIF>
>
> Others do:
> <CFTRY>
> <cfparam name="ID" type="numeric">
> <CFCATCH>
> You must pass a numeric ID
> </CFCATCH>
> </CFTRY>
Actually, there is a performance difference between them in theory.
try/catch introduces more overhead into the performance due to its
need to run, evaluate, and then test the various catch conditions for
a best match. With the isDefined(), it either exists or it doesn't.
Very simple and "brute force." Here are my two rules that I would
submit as best practices:
1) In CFMX 6 and 7, every internal scope is a struct, and, as such,
the struct-related functions have been heavily optimized. (I think
there were some exceptions for scopes like "cookie" in previous
versions.) Therefore, I almost never use isDefined() anymore, for
reasons that have been documented both here and on various blogs. My
team's standards dictate that structKeyExists() be used around checks
for all variables:
<cfif structKeyExists(variables, "id")>
...
</cfif>
<cfif structKeyExists(url, "id")>
...
</cfif>
The only time I can think of where I use isDefined() is in something
like an error e-mail where I want to check if there was a form scope
in the request that failed so that I can dump it or skip it.
isDefined() will go through every possible scope it can, including the
CGI scope to find the variable being checked. That puts a
(comparatively) noticeable overhead on the request as opposed to
targeting a specific scope or scopes. I might be forgetting another
one-off example, but you'll find most of the time that isDefined()
just isn't needed.
2) Put cftry/cfcatch around code snippets that rely on non-ColdFusion
technologies, and around snippets of code that can gracefully handle
an exception. I don't put it around each and every query because I
know that if a very basic query if failing, then I have bigger
problems that a try/catch isn't going to solve. However, we interface
with a lot of non-CF technologies at my company (i.e., Python external
methods, web services, etc.), and I don't necessarily have control
over their uptime or availability (for example). Therefore, I need to
be able to display a "system is down" message and/or send an e-mail to
myself as an alert. Other examples include POP and FTP access.
try/catch should be used only when necessary. As for the reply that
noted he has a developer who puts try/catch around everything,
education is the best remedy there. Have him research try/catch both
in LiveDocs and across the web to show why his approach isn't
recommended.
Regards,
Dave.
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