Model-View-Controller — Misunderstood and Misused

paradox1x writes "Malcolm Tredinnick shares a terrific rant against the misunderstanding and misuse of the Model-View-Controller design pattern. In particular he takes issue with the notion that Django should be considered an MVC framework. He says that 'It's as valid as saying it's a "circus support mechanism," since the statement is both true, in some contexts, and false in others (you can definitely use Django-based code to help run your circus; stop looking so skeptical).' I'm not sure I agree with the entire piece, but it is a very good read." We recently discussed another look at the bending and stretching of MVC patterns in the world of Web development.

Comments

Pedantry

[Anonymous Coward]

So let me get this straight: you're upset because some developers are misusing a term and giving their product more credit than it should have?

Well, that's never happened before!

Web Frameworks

[truthsearch]

The custom web framework my company uses helps program with the MVC pattern, but doesn't enforce it. Some developers are very consistent with separating the model, templating, and control structure. Some developers (not always the less experienced ones) often intermingle functionality and don't realize they're no longer within the MVC design. So our framework is nice that it's flexible, but it also will let you hang yourself. Most other frameworks, at least for PHP and Python, seem to be the same way.

Author is Pedantic

[iluvcapra]

And does quite a bit of complaining about Django without completely demonstrating his point. I'm still foggy about his complete idea of what he believes the original interpretation of a "Controller" is, which is really the heart of the matter and where most people seem to disagree. His "model" of what MVC is is not explicated in his view, as represented by his blog post.

MVC is a pattern, not a set of rules, a coding style, house style, development framework, or development process. If you have three modules, one doing presentation, one doing state, and one mediating, you're doing MVC. What specific functions go where (is sorting on the model? is validation of this field in the view?) is specific to the problem domain.

IMHO

Re:Author is Pedantic

[LaskoVortex]

I'm still foggy about his complete idea of what he believes the original interpretation of a "Controller"

It's always good to define one's terms before one begins to write about them. If you ask 10 different experienced developers what MVC is, you'll get 10 different answers. The problem with this article is that we never get what the author's interpretation of what MVC really is.

But no matter what one's definition of MVC, its like OOP. With OOP, it has been said that any substantially complex system is actually going to require some sort of implementation of OOP, even if its hopelessly half-assed. The same can be said for MVC.

Of course I just committed the same omission as TFA in that I haven't defined exactly what I mean by the terms I use.

Re:Author is Pedantic

[KDR_11k]

I think the idea is that the view is interchangeable and isn't expected to do anything in order to allow the system to function but it can of course have extra functionality that is not necessary but increases the userfriendliness. The view can validate the user inputs to spare the user some grief but the controller should never expect the view to behave in any way.

Re:Author is Pedantic

[lgw]

When I firt read Design Patterns 15-ish year sago, I was hoping for a book of insightful best practices, but instead found a bunch of ideas that were obvious to anyone skilled in the art, being given arbitrary names and then heavily obfuscated with UML. The majority of these "paterns" were things that were trivial to implement in (or just built into) other languages, but hard to do in C++. Somehow people thought this was ome major revelation. I still don't get that.

And IMO it did more harm than good, merely because people saw "singleton pattern" and reverted to heavy use of global storage claiming "it has to be OK, it's a design pattern". Sadly, that's the one that fresh college hires do seem to know.

Of course, I do work with device drivers and other "systems" code, not CRUD code, so maybe I'me just not in the right field to "get" these.

Django

[styrotech]

I was under the impression that the Django team don't consider it to be MVC themselves, but they've just given up the losing battle of explaining the difference to the masses who think that MVC is the only good way you can arrange 3 different tiers of an application. So they've shrugged their shoulders and effectively said "Fine. If you want Django to be MVC, it is MVC. Now drop it and let us get back to developing it.".

Wrong.

[Qbertino]

Author is Pedantic

No he isn't. He critisizes the incorrect use and application of the term MVC and the misconception and the pointless enforcement of a wrong concept of MVC in places where it is often more than pointless to do so. Like in most modern web application scenarious.

And does quite a bit of complaining about Django without completely demonstrating his point.

No he doesn't. He uses Django as an example for all current hip Web FWs out there to emphasise the issue above. And he clearly states that before he even goes into Djangos documentation and concept of MVC.

MVC is good

[bytesex]

MVC is good. When you understand it at its simplest. But it doesn't need a 'framework', which is where the confusion creeps in. Java is on the one hand so popular, yet so hopelessly constrained in its possibilities and libraries, that apparently this confusion seems to have become 'unrecognisable' as it were: people automatically postfix 'framework' behind 'MVC' because it's so difficult to build web-applications in java without one (well it's not, but they don't usually know that either).

A framework is a meta-language in essence, it 'sits on top' of your project. Libraries OTOH are (usually) written in your own language and 'hang below' your project (i.e. you use them, instead of it using you). Both can provide MVC, but both can provide many other things as well.

I prefer libraries me. I like to know where a request comes in, and be there when it happens. That said, libraries that model my data storage in nice structures and provide templating for output are yummy. But that's all - I feel the programming language should be *my* bitch, not the other way around. So yeah, I've had to write my own template rendering code since the existing ones all had unnecessary limitations rooted in the theory that the template shouldn't contain any code (so how are we supposed to go about iterations, theorists ?) or any complex variables (yet your data modelling library provides for those, thanks a lot !). Took all of a monday afternoon that.