There might be an even better way to do this (someone else made a similar
suggestion but I've already deleted the email). Instead of throwing an
exception within "getUser", return an "empty" user object. Then define an
"exists" method on the "userCFC" class that you could check after the
"getUser" call:
<cffunction name="getUser" returntype="userCFC">
...
<cfif doesUserExist>
<cfreturn theUser />
<cfelse>
<cfreturn emptyUser />
</cfif>
</cffunction>
Now you could call it like this:
<cfset user = getUser() />
<cfif user.exists()>
.. do stuff with user ..
<cfelse>
.. deal with invalid user ..
</cfif>
This is a lot better than throwing exceptions.
Vince
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Vince Bonfanti
> Sent: Sunday, October 23, 2005 9:34 AM
> To: [email protected]
> Subject: RE: [CFCDev] CFC return types
>
> Assuming that having a non-existent user is a normal part of
> your program flow and not an error condition, then no, this
> is definitely not the way you'd do it in Java. Using
> exceptions for normal (expected) program flow is considered
> bad practice and is also a performance killer (throwing
> exceptions in Java is very expensive). I'd recommend that you
> not to it in CFML either. Since CFML doesn't support the
> concept of null, a way around this without using exceptions
> is to define a "doesUserExist" method that you'd invoke first
> before calling "getUser". So a modified version of Barney's
> example would look like this:
>
> <cffunction name=doesUserExist" returntype="boolean">
> <cfreturn doesUserExistCondition />
> </cffunction>
>
> <cffunction name="getUser" returntype="userCFC">
> ...
> <cfif doesUserExist()>
> <cfreturn theUser />
> <cfelse>
> <cfthrow type="UserNotFoundException" />
> </cfif>
> </cffunction>
>
> Then you'd call it like this:
>
> <cftry>
> <cfif doesUserExist()>
> <cfset user = getUser() />
> .. do stuff ..
> <cfelse>
> .. deal with the invalid user ..
> </cfif>
> <cfcatch type="UserNotFoundException">
> .. deal with the invalid user ..
> </cfcatch>
> </cftry>
>
> You'll probably still want to keep your exception handling in
> place in case someone forgets to call "doesUserExist" before
> "getUser"--but that's now an error condition instead of
> normal program flow. The ultimate answer, of course, is that
> CFML should support the concept if nulls. In an earlier
> thread on this list I proposed the introduction of an
> "isNull" method, so that you could do this (again, a modified
> version of Barney's original
> example):
>
> <cfset user = getUser() />
> <cfif isNull( user )>
> .. deal with invalid user ..
> <cfelse>
> .. do stuff ..
> </cfif>
>
> (Yes, I expect we'll introduce the concept of null objects
> and the "isNull"
> function in a future version of BD).
>
> Vince
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Andrew Scott
> > Sent: Sunday, October 23, 2005 1:36 AM
> > To: [email protected]
> > Subject: RE: [CFCDev] CFC return types
> >
> > Is that the same way one should do it in Java as well?
> >
> > I sort of look at some code and see null or object being
> returned, and
> > guess have that stuck in my head.
> >
> > Thanks Barney / Sean.
> >
> >
> > Regards,
> > Andrew Scott
> >
> > Quote of the Day:
> > Felix's Wife: Dr. Connors. I want to thank you for
> fixing Felix's
> > back.
> > He can even help around the house again. Phil Connors: I'm
> sorry to
> > hear that, Felix -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Barney Boisvert
> > Sent: Sunday, 23 October 2005 3:24 PM
> > To: [email protected]
> > Subject: Re: [CFCDev] CFC return types
> >
> > Here's the skeleton of the function:
> >
> > <cffunction name="getUser" returntype="userCFC">
> > ...
> > <cfif doesUserExist>
> > <cfreturn theUser />
> > <cfelse>
> > <cfthrow type="UserNotFoundException" />
> > </cfif>
> > </cffunction>
> >
> > And then calling it:
> >
> > <cftry>
> > <cfset user = getUser() />
> > .. do stuff ..
> > <cfcatch type="UserNotFoundException">
> > .. deal with the invalid user ..
> > </cfcatch>
> > </cftry>
> >
> > Just for references, with a "null" return value the function would
> > return some kind of null instead of throwing the exception, and the
> > calling code would look like this:
> >
> > <cfset user = getUser() />
> > <cfif user is null>
> > .. deal with invalid user ..
> > <cfelse>
> > .. do stuff ..
> > </cfif>
> >
> > cheers,
> > barneyb
> >
> > On 10/22/05, Andrew Scott <[EMAIL PROTECTED]> wrote:
> > > Barney,
> > >
> > > If you don't mind I would like an example to clarify, in
> > this example
> > > I am checking to see if a user exists, it returns the user
> > object if it does.
> > So
> > > when it returns back to the caller how do I handle it, if
> > you can give
> > > me
> > an
> > > example to help clarify what your saying that would be much
> > appreciated.
> > >
> > >
> > > Regards,
> > > Andrew Scott
> >
> >
> > --
> > Barney Boisvert
> > [EMAIL PROTECTED]
> > 360.319.6145
> > http://www.barneyb.com/
> >
> > Got Gmail? I have 100 invites.
> >
>
>
>
>
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