The Developer Day | Staying Curious

TAG | mvc



Skinny Controllers and Fat Models

Most of the modern web application frameworks follow the MVC design pattern. It’s probably one of the most misunderstood design patterns in existence. There are a lot of discussions what kind of responsibilities each letter holds. Common misinterpretation in MVC is regarding the letter M.

The Model should be understood as a domain model. Meaning a collection of domain objects. Usually an application has one model that is the domain model. Models are often mistakenly referenced to as singular domain entities. For example an Order, a User or an Account. This leads unwary developers to common application design problems.

It’s common to see a web application to have a directory named “models” with class files inside it. Upon closer inspection one can often find that those classes are the nouns of the application. For example those nouns could be a User, an Order or a Product. In this scenario the MVC Model stands for singular application entities.

Problems start to surface when an application developer has to create reports, do input validation or to implement an ACL. These kind of problems don’t naturally fit into entities. For example getting a report of top 10 products doesn’t naturally fit into any entity. Validating a complex search filter made out of multiple input fields also doesn’t fit into any of the entities.

It’s common to see developers adding logic that doesn’t fit anywhere naturally to controller classes or somewhat close entities. For example adding a top 10 products report to an Order entity class as a static method call. Or validating complicated search filters inside controller actions.

In time this steadily leads to bloated controller and entity classes that later on become fat spaghetti dishes. Controller classes containing thousands of lines of code with more private methods than public ones, entity classes with few state changing methods and hundreds of lines long SQL report queries with joins to 10 tables.

To prevent this from happening it is crucial to understand what controller and model stands for. A controller’s responsibility is only to receive input and initiate a response for the view by making calls on model objects. This means that controllers should be very light and skinny. Usually doing nothing else just instantiating classes, getting data from the domain objects and passing it to the view. Model is not a singular entity and can consist of an entire web of interconnected domain objects. The definition fat model means having as many domain objects as needed. Be it reports, validators, filters, entities, strategies and so on.

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Sample PHP MVC application

Every web developer probably at some point heard something about MVC unless he or she was living in a cave. I definately have heard and read a lot about it. I won’t probably lie too much to say that most people know that MVC is the nowdays defacto design pattern for web applications. Atleast for PHP it is.

If you have ever had interest in design patterns and did some research on them you may know that design patterns may be interpreted and implemented different every time one tries to. And MVC is no exception to this rule. In my own career path I have seen many projects that claim to implement the MVC design pattern. And if it actually doesn’t - it may be called a hybrid of MVC. As ridiculous as it may be I think because of the MVC hype and everyone trying to be able to claim “yes we use MVC” it is one of the most misunderstood patterns of them all. And because of this … There are a LOT and i mean a LOT of articles and blogs and forums trying to explain MVC the way it should be.

And I myself have read a lot of versions of these blogs and articles. And to be honest I couldn’t answer to you for example what a controller should do and should not do. Well ofcourse I know it shouldn’t contain any business logic. If you would try to research that you would probaly find people saying that the controller should initiate the model, do something with the model and pass the result to the view and render it. You can even find some examples..

But to some extent I find it all synthetic and not very realistic. Most examples are of the level of Hello World program. I think the devil is in the details. If you would try to find any sample php mvc applications you probably wouldn’t find much. There are a few very simplistic sample MVC projects but I don’t find that to be an eye opener that goes deep into details.

I think the PHP community needs such an example. I believe Zend Framework is a great start for MVC. But it isn’t enough. It still doesn’t show you how a real life model or controller would look like. What each part of MVC would do and would not. I believe that one good example is better than a thousand words. I feel trully interested to try and find the “Equilibrium” of the famous MVC design pattern. Don’t you?

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Zend Framework pros and cons

Generally I dislike most PHP frameworks. Especially after the Ruby on Rails fashion wave after which a lot of PHP frameworks have been born with ActiveRecord implementations, scaffolding and so on. It makes you creep after watching yet another Blog development screencast in 15mins “using the best new framework”!

Not so long ago Zend Framework released a stable release and today I’ve spent my time at work watching screencasts and webinars to take a closer look at it.

And I LOVED IT :) Here’s why:

  • Whole framework is just one directory of classes that you don’t ever care about with no predefined application structure and design by default.
  • It stands behind a respectable and well known company ZEND that has a lot of to do with PHP.
  • It has an outstanding team of professional contributors with a lot of brain power and experience.
  • Lots of well developed components following actual design patterns.
  • 80% > unit test coverage
  • A useful documentation that most others are missing.
  • MVC components, controller plugins, helpers.
  • A possibility to develop a modular application where each module has it’s own views, controllers, models that can easily be removed by anyone in seconds while other frameworks force me to split MVC components to other directories and making it hard to separate from hundreds of others.
  • It does not have ActiveRecord and Scaffolding :)

Though there are some issues people might spot:

  • Zend_Controller_Helper_Abstract. Class names lack namespaces. Though there were no namespaces available while Zend Framework has been actively developed and does it really matter?
  • You need to understand a few design patterns and OOP to use full Zend framework’s potential. And that does not only requires time spent learning but also experience working with it.
  • It is big, it is heavy, it eats memory and it has a lot of includes. Though I usually tend to agree with the “hardware is cheaper than development” theory ..

All in all I find Zend Framework the best PHP framework there is. In the past I looked at CakePHP, symfony, code ignite. I’m going to give Zend Framework a try at work and implement a not so very important project with it. If it works out well I might start migrating all our frameworkless applications to it.

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