Wondering about MVC

[BSCode266]

Hey all,

I was kinda wondering about how many people here have actually used or are using the Model-View-Controller-model. Is it really usefull?

for those who wonder what MVC is: http://en.wikipedia.org/wiki/Model-view-controller

BSCode266

[hirak1984]

yes many here are using/had used MVC

all the standard frameworks are based on this model.
but why are u asking?
do you have a better design to write codes?
please let us know...

Hey all,

I was kinda wondering about how many people here have actually used or are using the Model-View-Controller-model. Is it really usefull?

for those who wonder what MVC is: http://en.wikipedia.org/wiki/Model-view-controller

BSCode266

[BSCode266]

yes many here are using/had used MVC

all the standard frameworks are based on this model.
but why are u asking?
do you have a better design to write codes?
please let us know...

Well they tried to teach it to me in school, but some the teacher didnt show up 2 out of 4 classes so i started wondering is it worth learning. After a while i have been trying to understand it but without someone properly teaching it to ya its kinda hard to find out. Right now i am making an old assignment of a microwave in mvc or at least i think i do. So i thought i'd ask.

What do you mean with all the standard frameworks? And would the MVC-model be the best way to do it?

BSCode266

[JosAH]

Personally I never allow my Views to talk with the Model directly.This changes
the triangle shaped pattern to a simple bidirectional pipeline:

View <-------> Controller <-------> Model

... and turns the Controller classes into a simple more Mediator like pattern
and it keeps the View as stupid as possible (which is AGT (A Good Thing (tm)).

kind regards,

Jos

[BSCode266]

Personally I never allow my Views to talk with the Model directly.This changes
the triangle shaped pattern to a simple bidirectional pipeline:

View <-------> Controller <-------> Model

... and turns the Controller classes into a simple more Mediator like pattern
and it keeps the View as stupid as possible (which is AGT (A Good Thing (tm)).

kind regards,

Jos

I see, but then how do you update your view? Isnt view supposed to update according to the model? do you give this task also to the controller?

Another thing, Controller is just supposed to handle input right? so then if you would change your controller in an eventhandler this wouldnt be wrong?

And what about something called an Observer? i kinda came across this in a powerpoint explaining MVC but have no idea what it is or does.

I have attached the uml. Sorry about the poor quality.

[JosAH]

I see, but then how do you update your view? Isnt view supposed to update according to the model? do you give this task also to the controller?

Yep, for simple things the Controller just passes it along from the Model to
the View. For more complicated things the Controller should be the destination
of the fired event anyways.

Another thing, Controller is just supposed to handle input right? so then if you would change your controller in an eventhandler this wouldnt be wrong?

I wouldn't be wrong, both the Model and the View generate events and the
Controller catches them all and decides what to do with them.When the View
fires an event the user was the actual cause. When a Model fires an event it
was just because some data changes or some business status has changed.
Let the Controller handle it and update the View/Model whenever necessary.

And what about something called an Observer? i kinda came across this in a powerpoint explaining MVC but have no idea what it is or does.

An Observer is the same as a Listener (in Java speak). The Observer simply
listens for events fired by an Observable. The pure Observer/Observable
implementations in Java are next to useless given the fact that the
PropertyChangeSupport class can handle it in a far more flexible way.

kind regards,

Jos

[hirak1984]

Thinking in this way definitely helps.

I myself use this model.

Personally I never allow my Views to talk with the Model directly.This changes
the triangle shaped pattern to a simple bidirectional pipeline:

View <-------> Controller <-------> Model

... and turns the Controller classes into a simple more Mediator like pattern
and it keeps the View as stupid as possible (which is AGT (A Good Thing (tm)).

kind regards,

Jos

[hirak1984]

well according to the new definations of M,V,C


View is the part that listenes to the change in model.(and renders it to the viewer)
Controller helps in select the appropriate view.
Model talks to the database.
Observer helps in selecting the appropriate model(it is like an array of models).

I see, but then how do you update your view? Isnt view supposed to update according to the model? do you give this task also to the controller?

Another thing, Controller is just supposed to handle input right? so then if you would change your controller in an eventhandler this wouldnt be wrong?

And what about something called an Observer? i kinda came across this in a powerpoint explaining MVC but have no idea what it is or does.

I have attached the uml. Sorry about the poor quality.

[JosAH]

Thinking in this way definitely helps.

I myself use this model.

I like it too with the communication between a View and Model cut away
from the pattern. There are perfect examples why this makes sense; e.g.
JSPs dealing with a database directly are considered a big nono. JSPs
are for views, not for model fiddling. I for one don't even understand why there
is database support in the JSTL (its 'sql' tags). It is bad practice especially
when separate tiers are involved. And above all: those 'sql' tags assume that
I want to work using sql which I don't because it's extremely primitive compared
to object oriented databases available nowadays ;-)

kind regards,

Jos

[BSCode266]

Thanks guys, this sure made it alot clearer. Now i understand why they want me to use it. Should one always try to use this, i mean is it some sort of standard that you make bigger programs with MVC?

BSCode266

[JosAH]

Thanks guys, this sure made it alot clearer. Now i understand why they want me to use it. Should one always try to use this, i mean is it some sort of standard that you make bigger programs with MVC?

BSCode266

Well, that MVC stuff is 'best practice' which is one of the prerequisites to make
it a pattern. If someone comes up with something better I think it's better to
use that something else. But it always makes sense to 'separate concerns'
(another OO mantra) so it's a good thing to separate the I/O from the business
logic and separate that from your (data) model; no matter how small your
application is.

kind regards,

Jos

[hirak1984]

Well can you give some more ideas about object oriented databases...

I am totally unaware about them.

I like it too with the communication between a View and Model cut away
from the pattern. There are perfect examples why this makes sense; e.g.
JSPs dealing with a database directly are considered a big nono. JSPs
are for views, not for model fiddling. I for one don't even understand why there
is database support in the JSTL (its 'sql' tags). It is bad practice especially
when separate tiers are involved. And above all: those 'sql' tags assume that
I want to work using sql which I don't because it's extremely primitive compared
to object oriented databases available nowadays ;-)

kind regards,

Jos

[JosAH]

Well can you give some more ideas about object oriented databases...

I am totally unaware about them.

Check out Cache (with an accent-aegue (sp?)) on the 'e' by Intersystems.
That DB is a lot of fun to work with, especially their 'Jalapeno' technology
that allows persistence of your POJOs (Plain Old Java Objects) without the
need of all that OR mapping stuff. As far as I can tell now the DB scales
well too which is another advantage (I must confess) I didn't exprect.

My prediction is that all that clumsy Object-Relational mapping is doomed
to disappear very soon (except for those darn legacy applications) and that
might well take away all those clunky entity beans and those silly QLs.

kind regards,

Jos

ps. I'm not related to Intersystems whatsoever and I'm sure other companies
have come up with similar technologies as well.

[hirak1984]

hey thnx... surely will check them out...

Check out Cache (with an accent-aegue (sp?)) on the 'e' by Intersystems.
That DB is a lot of fun to work with, especially their 'Jalapeno' technology
that allows persistence of your POJOs (Plain Old Java Objects) without the
need of all that OR mapping stuff. As far as I can tell now the DB scales
well too which is another advantage (I must confess) I didn't exprect.

My prediction is that all that clumsy Object-Relational mapping is doomed
to disappear very soon (except for those darn legacy applications) and that
might well take away all those clunky entity beans and those silly QLs.

kind regards,

Jos

ps. I'm not related to Intersystems whatsoever and I'm sure other companies
have come up with similar technologies as well.