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Hi
Nando,
Agreed
100% with everything except for the idea that having a facade to the model
creates spaghetti code.
There
are two distinct functions the controller usually handles in an HTML app - all
the HTML specific stuff, and orchestration. If you have only one controller
layer that always calls functions to get session information, check for cookies
and the like, try calling that using a web service or flash remoting and see
what happens. Of course, you could replicate your orchestration code in the
flash movie and in your HTML controller and have flash access your model
directly, but then if your business rules for orchestration changes, you have to
change them in two places.
To me,
it just makes perfect sense to have a facade to handle orchestration and to have
a seperate controller to handle all of the HTML specific stuff if you're ever
going to expose your business methods to non-HTML consumers. And it's not like
this is a pattern or approach I made up out of thin air - I'd say it's a pretty
well established pattern for enterprise architecture.
While
you're pointing to resources, I'd also add Martin Fowler for some less CF
specific, but interesting articles.
Best
Wishes,
Peter
Ummm ... something to say here.
What
you'll *always* need, no matter how you break your code apart, is some bit of
code that tells the other bits what to do and when to do it.
Now, you
can spread that out all over the place, CodeChunkA tells CodeChunkB to do
something and then CodeChunkB tells CodeChunkC and CodeChunkD to do something,
and then CodeChunkA tells CodeChunkE and F to do something and so on until you
get to CodeChunkZCZR ... but then when you or someone else comes along in 5 or
6 months and looks at that, they'll have a really hard time figuring out how
it all works.
Coding in this style has come to be known in some
circles as "pasta" of the long stringy kind. Spaghetti. It's a very Italian
way of dealing with things. Everybody tells everybody else what to do. (Ciao
Massimo, just joking a little! Don't take me seriously ;-)
So in the
example above, we don't have a single (or several) well defined controller(s),
but we still have chunks of code telling other chunks of code what to do and
when to do it.
So ... you always need that "hey you, do this" stuff in
your code. The only question is if you encapsulate it in one place, or spread
it all around.
Many programmers, even Italian ones, seem to feel after
a few years of experimentation that they are much better off encapsulating
that necessary "hey you, do this" stuff in one place in their code, so they
can easily come back to it down the line and see fairly quickly how the whole
thing works.
So no, you don't need *A Controller*, but you will always
need chunks of code telling other chunks of code what to do.
Nando
:)
PS ... A good way to understand how a controller works is to take a
good look at model glue. The controller is implemented in a very simple and
straightforward way as ModelGlue.xml and the controller cfc's. I don't think
many of us on this list would be able to implement a decent MVC app from
scratch without a framework to guide us. So i wouldn't start there, unless you
are very gifted at implementing abstract ideas in code from scratch.
I
have a friend who teaches artistic painting classes. He always has someone in
the class who comes up to him and tells him they're having trouble coming up
with something to paint. So he tells them, always, "Relax, Just copy what i'm
doing." And he turns the painting he's working on and points at it with a
smile so the student has a good view of it.
The student goes back and
starts copying. But the funny thing is, my painter friend tells me with a big
grin on his knowing face, "they always paint something totally
unique."
The only trick out here is to choose carefully who you "copy"
from! Here's a short list from this copy cat:
Hal Helms (his
newsletters)
Joe Reinhart (his tutorials but you have to search his blog
for them, the arf framework, the model glue framework)
Sean Corfeld (his
sample apps)
Ben Edwards (the machII framework)
Once you've been
copying for awhile, if you're gifted, you might graduate to being an
originator. But don't worry if it takes you a little while to get there.
:)
Peter Bell wrote:
Yep. Controller is indeed traffic cop. Also, if there is EVER any chance of
a non-HTML interface to your site (web services, flash remoting, whatever),
you will want two elements to the controller. A "framework" piece will
handle the junk you need to handle to read and speak HTML with a web browser
and the "orchestration" piece will call the right model methods in the right
order based upon business rules in a way that does not assume there is a
HTML request (think sessions, cookies, form variables, URL variables, HTML
as part of the response messages, etc.).
Best Wishes,
Peter
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf
Of Aaron Roberson
Sent: Friday, June 09, 2006 3:19 PM
To: CFCDev@cfczone.org
Subject: Re: [CFCDev] Do I Really Need A Controller?
So, you are saying that I should submit my form to the controller, and then
the controller will run the email evaluation and send an error if not valid,
or pass the form structure to the service to be inserted in the database if
the email is valid. Is that correct?
>From what I gather from your example, I think I am beginning to see how the
"traffic cop" works...
-Aaron
On 6/9/06, Dustin Tinney <[EMAIL PROTECTED]> wrote:
In that case my controller would have somethign like this...
if(NOT hasValidFields(attributes.form))
{
redirectToErrorPage();
}
model.storeInformation(attributes.form);
sendConfirm(attributes.form.email);
On 6/9/06, Aaron Roberson <[EMAIL PROTECTED]> wrote:
I just send a confirmation email, I don't really want to test the
visitor to see how badly they want my newsletter... ha, ha.
-Aaron
On 6/9/06, Dustin Tinney <[EMAIL PROTECTED]> wrote:
Do you send your user a "verify" email or a "thanks for
subscribing email"?
On 6/9/06, Aaron Roberson <[EMAIL PROTECTED]> wrote:
I have an email subscription form on my website that visitors
can fill out and subscribe to our newsletter. I have created a
subscriberBean.cfc with getters/setters and an email validation
method, a subscriberDAO.cfc with CRUD methods, and a service
that creates a DAO object and a gateway object and passes
arguments to the DAO and the gateway (this is all based on Matt
Woodwards
CF.Objective() example and Peter Farrell's code examples from
CFWeekly
1.10).
It seems to me like the view would interact with the service,
which would perform my CRUD operations and return my the query
results from my gateway. If so, what do I need a controller for?
I've heard that controllers act as traffic cops, but I'm not
sure what that means. If my view is validating form field
entries, and my model is validating form field entries, and my
view is getting everything it needs from the service layer, what
do I need a "traffic cop" for?
Thanks for your feedback and suggestions!
-Aaron
On 6/9/06, Dustin Tinney <[EMAIL PROTECTED]> wrote:
Yes would be the answer to your question about needing a
Controller. However with out knowing what your doing a little
more It's hard to give direct examples of WHY you need it.
On 6/9/06, Aaron Roberson <[EMAIL PROTECTED]> wrote:
I have been plunging head first in to OOP (into a wall, I
should
say...) and I am trying to put all the pieces together so that I
can
begin implementation.
Anyways, I am wondering if I need a controller layer in my
design pattern? I really don't like the idea of using a
configuration file (xml or index.cfm) and wiring everything
to it like a fusebox, so I am staying away from frameworks.
I have been learning about seperating my business model into
beans, DAO's, gateways and services and I think I like the
abstraction that offers. However, it seems to me like my
views can interact directly with the service, making a
controller layer unneccesary. Is that correct, or am I lost
again?
P.S. I don't entirely understand what all a service does, so
I do have some questions about the service layer, but I will
start a seperate thread for that. I would have some
questions about the facade layer, but I don't have a clue
how to use that so I don't even know where to begin with the
questions regarding that.
Thanks,
Aaron
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