There is a pattern called "Null Object", if I remember correctly. I use it
quite a bit, especially in regards to security. The component can either be
the same component that you usually return or a completely separate
component which implements the same interface.
For instance, if you're building a security system, you don't want to do
this everywhere:
<cfif isUserAuthenticated() and Session.User.IsUserInGroup(Group)>
...
</cfif>
It's much cleaner to use the Null Object pattern and have a User component
that always returns "false" when IsUserInGroup() is called. When the user
logs in, the Null Object is either replaced with a fully initialized object
that knows what to answer when IsUserInGroup() is called. Or, the User
component could double as the Null Object itself and the default answer to
IsUserInGroup() is always "false". Either way, your code looks like this:
<cfif Session.User.IsUserInGroup(Group)>
...
</cfif>
However, if you have to use two separate components, then they will have
different names and, as a result, the returntype attribute will need to be
set to "any". So, it doesn't solve much in the way of type checking.
Ben Rogers
http://www.c4.net
v.508.240.0051
f.508.240.0057
________________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Jared Rypka-Hauer - CMG, LLC
Sent: Thursday, May 12, 2005 7:46 PM
To: [email protected]
Subject: Re: [CFCDev] Null values (was CFC wish-list)
Barney...
I get your point, but I wonder... and prepare yourself for YACFOOWA (yet
another cf-oo work-around).
Why note just have a CFC called... null.cfc. If you need a standard,
consistent value to test against perhaps expecting the language to provide
it by default isn't always the answer.
If you had a null.cfc, you could actually USE type="null" or
returntype="null" in your CFC code. I'm not sure I understand the need for
making CF into something that it isn't, wasn't, and really probably never
will be. I can see adding interfaces being as easy as adding an
implements="" attribute to a CFC... but adding types to a loosely typed
language strikes me as an odd fix to a non-problem.
Maybe I'm missing something... if so, please point it out. I just see many
of these things that people are calling "deficits" as part-and-parcel to the
strength and core values of the language: flexibility and a focus on runtime
over compiletime.
Just my two cents since we're on the topic.
Laterz!
J
On 5/12/05, Barney Boisvert <[EMAIL PROTECTED]> wrote:
> In many instances, allowing functions to return null values just shifts
the
> problem or, at least, the responsibility. This is why we so many null
> pointer exceptions from Java and C#. They are proper OO languages
returning
> null values that the consumer is unprepared to handle.
I HAVE to respond this statement.��Having or not having null doesn't
affect this issue at all.��If i have null, I return it.��If I don't
have null, I return "something" (like the empty string).��In either
case, the calling code needs to be able to handle both scenarios.
Having null makes this easier, because you have a specific value to
test against, and more importantly, it's a value that cannot be
confused with any other value.
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