Posts filed under ‘mvc’

How to Beat Rails

(Note: I really, really like Ruby and Rails. Anything disparaging that I say about either of them should be taken with several grains of salt. If I seem to be encouraging Pythoneers to crush Rails, it’s simply because I love both, and want all frameworks to be constantly innovating.)

Everybody with the slightest interest in web development has heard of Ruby on Rails. It thrust Ruby into the spotlight, created a hype machine that stubbornly refuses to go away, and made David Heinemeier Hansson a celebrity. I adore Rails – it’s by far the best web framework for simple CRUD apps. However, as a Python devotee, it hurt me deeply to see Ruby stealing the spotlight. As such, I embarked on a quest to find out why Rails is winning; I looked at Django, Turbogears, Pylons and web.py. After months of building the same simple CRUD app, I came to the following conclusion:

Python can beat Rails. It can grind it into a pulp in every way concievable – speed, elegance, coolness, extensiblity, organization, AJAXness, beauty, and flexibility. It can send Rails crying home to David while Guido basks in the Web 2.0 spotlight. But right now, Rails is thoroughly torching all of the Python web frameworks. The following is a list of recommendations that, if applied to a Python framework, could dislodge Rails from the position of King of the Web Frameworks.

(more…)

December 31, 2006 at 10:17 pm 26 comments

mogenerator, or how I nearly abandoned Core Data

Unfortunately, my Macbook Pro is out of commission due to a broken fan (I’ve sent it in to Apple; they’d better send it back soon! I’m dying here!), so I’m just going to blog about a mini-renaissance I had when working with Core Data last week.

When I first saw Core Data, I couldn’t believe my eyes. Apple’s developer tools now had a simple way to graphically model as many parts of an MVC application as possible – Interface Builder for the view, Cocoa Bindings (and custom logic) for the controller, and now Core Data for the modeling. Add in the fact that I had heard nothing but praise for it, and I was completely sold. I created the model for my application, prototyped a view, and flipped to the documentation on Core Data’s NSManagedObject.

It was, to say the least, an unpleasant surprise. Though I adored the fact that Core Data would take care of undo/redo, saving, archival formats, and saving data, I didn’t want to start using valueForKey:. setValue: forKey, primitiveValueForKey:, and setPrimitiveValue: forKey: instead of the mutator methods that I had grown to love for their combination of ease-of-use and added maintainability. Sure, I could have made a million subclasses of NSManagedObject, but the idea of doing that manually struck me as tedious – and if there’s anything I loathe, it’s tedium. And updating every object every time I made a change to the Core Data model struck me as a maintainability nightmare.

Though it may reflect poorly on me as a programmer, I considered abandoning Core Data. The magic which it brought to undo/redo/saving/archiving could not overcome the reluctance I had to view all my objects as NSManagedObjects – which, frankly, seems like quite a breach of the Model part of the MVC philosophy.

But hope lay in wait. At the bottom of some Google results about subclassing NSManagedObject, I found this page from Jonathan ‘Wolf’ Rentzsch – one of my idols, both for his coding and his vocal pro-Cocoa advocacy – about an unbelievably clever tool named mogenerator.

In short, mogenerator reads the data you have stored in an .xcdatamodel file, extracts the information about each Entity one has created, creates two subclasses of NSManagedObject for each Entity, changes the .xcdatamodel file automatically so that your Entities inherit from their proper classes, and adds code for all necessary accessor and mutator methods – in short, it removes everything I resented about Core Data.

Why two subclasses? Because if I decide to make a change to the data model, I don’t wont to worry about overwriting my own code with the automatically generated code that mogenerator creates for me. To solve this problem, Wolf has his program use one of the two files for automatically generated code, and allows one to use the second – which extends the first file’s class – for one’s own nefarious purposes. If you ever update the .xcdatamodel file, all you need to do is run mogenerator again, and only the file with the automatically generated code will be overwritten; you can be sure that the custom application logic you’ve written will stay intact.

This is a stunningly useful program, and I don’t know why people aren’t proclaiming it’s merits hither and yon. mogenerator allows one to forgo all compromise with Core Data – you get all the advantages of an NSManagedObject without sacrificing the familiar paradigm of creating specific .c/.h files for each object’s code. My thanks go out to Rentzsch for such an amazing tool.

December 19, 2006 at 6:24 pm 4 comments

It’s Hard Out Here for an MVC Advocate

Edit: I finally got the Interface Builder palette mentioned herein working. I’ll post a screenshot sometime later. I also cleared up some language.

In the past, I have alluded to the fact that I am a diehard Model-View-Controller advocate. I stay remarkably lax on other issues – I don’t mind breaking encapsulation, enjoy both static and dynamic typing, and even advocate paradigms other than OOP for certain applications. However, when it comes to GUI or web application development, I will defend Smalltalk’s Model-View-Controller paradigm to the death. In my still-inchoate Cocoa application, I’m using Interface Builder for the view, Core Data for the model, and Cocoa Bindings + my own code for the controller.

The problem emerges when I need to use the smattering of custom widgets that I’ve selected. Since creating Interface Builder palettes is so difficult, it’s hard to get people to make them – but MVC falls apart the moment you have to exit out of Interface Builder to make visual changes to your own instances of custom widgets.

Therefore, I am stuck with a hard decision. Do I break the MVC design pattern and make a zillion little subclasses of NSView, in which I stick a whole bunch of initialization code? It would be a lot easier, especially when one considers how hard it is to create an IBPalette.

But it’s so ugly! I don’t want a custom-made NSView subclass for each color CTGradient that I want! And until Chad Weider releases a CTGradientWell (please, please, please, pretty please?) making a PTGradientView will be quite difficult.

Bah. Any comments/help/IB Palettes will be appreciated.

December 6, 2006 at 5:47 pm 5 comments

Worse is Better: Python templating systems vs. Rails ERb

(Disclaimer: Python is my favorite programming language; however, I do criticize it in this article. Please redirect flames to /dev/null.)

I’ve been comparing web frameworks lately, developing a relatively simple CRUD database-backed application that can support a few bells and whistles. I’ve checked out Ruby on Rails (who hasn’t?) Django, and Turbogears in my search, and realized something as I was hacking together some templates in Kid:

Python, a far more restrictive and inflexible language – one that would seem, on the surface, to be worse for web application development than Ruby – is better for programmers, designers and security by nature of its inflexibility.

Let me explain what I mean. When designing ‘views’ – the web pages that users will see – that need to be updated with data from a given database, it is natural to break the Model-View-Controller paradigm and embed some controller logic into the application. After all, it’s so much less effort to embed

<% found_books = Book.find_all(“title = ?”, given_title) %>

into your .rhtml files then to go back into the controller file, change the return types, and make sure everything works correctly. However, Python is whitespace-sensitive, and therefore is much more difficult to embed into HTML. As such, you can’t write the mixture of Ruby and HTML that makes Rails so easy to use.

This is a good thing. I am a strong advocate of separating the model, view, and controller; by the very fact that I can’t write a combination of Python and HTML, I am forced to go back into the CherryPy/Django controller codebase and write a properly formed, secure, and elegant SQL query. Normally laxity wouldn’t bother me, but I believe that any large web application will grow into a hideous, Nylartothepic tangle if the MVC rules are not followed to the letter.

I still love Rails, but I love the templating systems in Python even more. Because Python is so restrictive, people had to write templating systems the Right Way – and that’s a good thing for everybody.

December 3, 2006 at 6:42 pm 1 comment


About Me



I'm Patrick Thomson. This was a blog about computer programming and computer science that I wrote in high school and college. I have since disavowed many of the views expressed on this site, but I'm keeping it around out of fondness.

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