TweetFollow Us on Twitter

The Philosophy of Cocoa: Small is Beautiful and Lazy is Good

Volume Number: 18 (2002)
Issue Number: 8
Column Tag: Mac OS X

The Philosophy of Cocoa: Small is Beautiful and Lazy is Good

by Andrew C. Stone

I believe a programming renaissance is upon us--and Cocoa, Apple's high level object-oriented framework is at the heart of it. By wrapping complexity inside easy-to-use objects, Cocoa frees application developers from the burden of the minutiae that so often drives developers crazy. Instead, they can focus on what's special about their applications, and in a few lines of code, create a complete OS X application that seamlessly interoperates with all other OS X applications. And, for very little additional effort, they get AppleScriptability as well.

I've been living and breathing Cocoa and its various previous incarnations for 14 years now, and have noticed that my applications are getting more features with smaller amounts of code each year. This article will explore some of the truisms and gems hard earned by hanging in the trenches lo these many years.

Small is Beautiful

It's no coincidence that we use the term "architecture" for the overarching structure of an application. I received my baccalaureate in classical Architecture in the '70's when the visionaries of the time were rebelling against the huge concrete boxes that crushed the human scale and spirit. E. F. Schumacher, in Small is Beautiful -- A Study of Economics as if People Mattered:

    "What I wish to emphasise is the duality of the human requirement when it comes to the question of size: there is no single answer. For his different purposes man needs many different structures, both small ones and large ones, some exclusive and some comprehensive. Yet people find it most difficult to keep two seemingly opposite necessities of truth in their minds at the same time. They always tend to clamour for a final solution, as if in actual life there could ever be a final solution other than death. For constructive work, the principal task is always the restoration of some kind of balance. Today, we suffer from an almost universal idolatry of giantism. It is therefore necessary to insist on the virtues of smallness - where this applies. ..." (p. 54)

I believe this thinking still rings true 30 years later in cyber-architecture.

From the programming classic The Mythical Man Month by Frederick P. Brooks, Jr., we learned that the more programmers you throw at a project, the less likely the project will ever be finished! From this follows that a project should have one central architect, with rather fascist control over feature set and implementation, especially if you want it to ship in a timely fashion. Cocoa gives you the tools needed to build full-featured, world-class applications with just a handful of programmers. For best effect, these programmers should be lazy...

Lazy is Good

Laziness is a virtue, believe it or not! I often describe my style of a computer scientist as someone who is so lazy that they'll spend days writing software to save a minute each time the task is performed from then on. There are two forms of laziness that Cocoa embraces: lazy loading of objects and just plain lazy programming.

Bundle it Up

Lazy loading lets full-featured applications like Stone Design's Create(R), a three-in-one illustration, page layout and web authoring app, launch in just a few seconds. Compare that to a legacy Carbon application with half the features which takes minutes to launch! By using dynamically loaded bundles, you do not use memory or resources until the end user actually needs that particular feature and its related resources. Moreover, you can update and distribute just the tiny bundle instead of the whole application should, heaven forbid, a bug be found!

To use dynamically loaded bundles, you need to be able to compile your application without actually referencing the loadable object directly. We do this runtime magic by only referring to the dynamically loaded class, the principal class of the bundle, by its name as a string.

Typically, the types of objects that do well being loaded dynamically are the numerous special editors and interfaces in a program, such as an arrow or pattern editor and the classes it needs to provide the interface. The following conditions make up a good candidate for a loadable bundle:

  • Has resources that are not always used each session

  • Doesn't contain core data model classes (these should be linked)

A typical example might have an NSWindowController subclass and perhaps some custom views and images in the bundle. We load this type of bundle by having it respond to the class method "+sharedInstance", since you usually only need one of these objects per application:

- (void)loadAUniqueInterfaceObjectAction:(id)sender {
    // we only use the name of the bundle, not its class
    // which would cause an undefined symbol when linking:
    [[[NSApp delegate] sharedInstanceOfClassName:@"MyUniqueController"] showWindow:self];
}

But, with the introduction of sheets, two or more documents may want to load the same bundle (for example, a custom zoom sheet) at the same time. In this case, you'll want a unique instance, which will be released after use. These principal classes of bundles need only respond to -(id)init, which all objects do anyway since they inherit from NSObject which implements -(id)init;

- (void)loadAPerDocumentInterfaceObjectAction:(id)sender {
   [[[NSApp delegate] instanceOfClassName:@"MyPerDocumentController"] showWindow:self];
}

And, because we are lazy and more importantly, good programmers, we filter both of these methods through one factored method, -(id)instanceOfClassName:(NSString *)name shared:(BOOL)shared like this:

- (id)sharedInstanceOfClassName:(NSString *)name
{
    return [self instanceOfClassName:name shared:YES];
}
- (id)instanceOfClassName:(NSString *)name {
   return [self instanceOfClassName:name shared:NO];
}

And here's the non-linked bundle loading code for both of them, which we place for convenience in the globally available [NSApp delegate] class:

- (id)instanceOfClassName:(NSString *)name shared:(BOOL)shared
{
    id obj = nil;
    NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"bundle"];
    if (path) {
        // we found the bundle, now load it:
        NSBundle *b = [[NSBundle allocWithZone:NULL] initWithPath:path];
       // if it loads, see if it has a valid principalClass - this is set in PB's target inspector
        if ((b != nil) && ([b principalClass] !=NULL)) {
     // here is the only difference between a single shared instance
     // and a new one every time:
            if (shared) obj = [[b principalClass] sharedInstance];
            else obj = [[[b principalClass] allocWithZone:NULL] init];
        } else {
   // This is for debugging in case it can't be loaded:
   NSLog(@"Can't Load %@!\n", path);
        }
    } else NSLog(@"Couldn't find %@ bundle!\n",name);
    return obj;
}

Code Lazily

Lazy programming means "Use the 'Kit, Luke!" Every standard data structure and a complete set of API's are already available to you, so there is rarely a need to reinvent your own. Therefore, this lazy programming axiom has a corollary:

If it's hard to do or understand, it's wrong

By this I mean any coding solution that involves convoluted logic or going beneath the API (using undocumented methods) is probably not the right approach. Taking the time to understand what's already offered to you is well worth the effort, because Cocoa, and its underlying frameworks, Foundation and AppKit, have evolved over 16 years to provide the basic building blocks of an object oriented solution. Many times when I'm adding a new feature, I'll try one brute force approach, notice how cumbersome it is, re-read the AppKit or Foundation API and find a much a better solution involving much less code.

For example, I recently added a "Clone Client" feature to TimeEqualsMoney(TM) - take the current document's data, remove the individual time entries, create a new document with all the same settings except no time entries. It was six lines of code and it worked the first time:

- (void)cloneDocumentAction:(id)sender {
    // make a new untitled - have it read our document:
    NSMutableDictionary *doc = [self workDocumentDictionary];
    MyDocument *newDoc = [[NSDocumentController sharedDocumentController]
openUntitledDocumentOfType:DocumentType display:NO];
    [doc removeObjectForKey:WorkKey];
    [newDoc loadDataRepresentation:[[doc description] dataUsingEncoding:NSASCIIStringEncoding] 
    ofType:DocumentType];
    [newDoc makeWindowControllers];
    [[[newDoc windowControllers] objectAtIndex:0] showWindow:self];
}

Instead of hiring programmers, why not let the entire Cocoa team at Apple be your engineers? When you use the Kit and Apple puts in new functionality and bug fixes, your application automatically gains these features and fixes. Your efforts should be focused on creating a mapping between the real world problems you are solving and the objects that represent them. Which brings me to my next point:

Put The Code Where It Belongs

One of the biggest challenges facing newcomers to Object Oriented Programming is placing code in the right object. Because many of us grew up with "procedural" languages like Basic, Pascal, and C, and because old habits die hard, we need to let go of trying to tell things what do to do, and instead, let them figure it out for themselves. Let's say we have a document which is a list of pages, which contains a list of graphics, which are simple graphics or groups, which contain a list of graphics, which are graphics or groups which contain, etc... And let's say we want to set the "isVisible" state of all the graphics in the document.

The procedural approach would be to assume absolute knowledge over this hierarchy, and you'd blithely code something like this:

@implementation MyDocument
// please don't do this!
- (void)setAllObjectsVisible:(BOOL)isVisible {
    unsigned int i, pageCount = [_pages count];
    for (i = 0; i < pageCount; i++) {
        Page *p = [_pages objectAtIndex:i];
        NSArray *graphics = [p graphics];
        unsigned int j, graphicsCount = [graphics count];
        for (j = 0; j < graphicsCount; j++) {
            Graphic *g = [graphics objectAtIndex:j];
            if ([g isKindOfClass:[Group class]) {
                NSArray *groupGraphics = [g graphics];
                unsigned k,groupGraphicsCount = [groupGraphics count];
                for (k = 0; k < groupGraphicsCount; k++) {
   // since this only recurses one level, this code is wrong as
   // well as very hard to read and maintain!!!
   Graphic *groupedGraphic = [groupGraphics objectAtIndex:k];
   [k setVisible:isVisible];
                }
            else [g setVisible:isVisible];
        }
    }
)
// the OO way:
@implementation MyDocument
- (void)setAllObjectsVisible:(BOOL)isVisible {
     [_pages makeObjectsPerformSelector:@selector(setAllObjectsVisible:) withObject:(id)isVisible];
}
...
@implementation Page
- (void)setAllObjectsVisible:(BOOL)isVisible {
     [_graphics makeObjectsPerformSelector:@selector(setVisible:) withObject:(id)isVisible];
}
....
// groups need to recurse down the hierarchy until individual graphics
// are found...
@implementation Group
- (void)setVisible:(BOOL)isVisible {
    [_graphics makeObjectsPerformSelector:@selector(setVisible:) withObject:(id)isVisible];
}
@implementation Graphic
- (void)setVisible:(BOOL)isVisible {
   // only do work if you absolutely have to - remember LAZY!
    if (_isVisible != isVisible) {
   // you'd probably do undo manager stuff here
   _isVisible = isVisible;
   // alert page we need to be redrawn
   [self tellMyPageToInvalidateMyBounds];
    }
}
...

Conclusion

The more you understand object oriented programming and Cocoa, the smaller and more reusable your applications will become. And they will load with lightning speed! But more importantly, you'll have less code to maintain which means less bugs, less headaches and more time to enjoy life.


Andrew Stone, CEO of Stone Design, www.stone.com, has been the principal architect of several solar houses and over a dozen Cocoa applications shipping for Mac OS X.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Top Mobile Game Discounts
Every day, we pick out a curated list of the best mobile discounts on the App Store and post them here. This list won't be comprehensive, but it every game on it is recommended. Feel free to check out the coverage we did on them in the links... | Read more »
Price of Glory unleashes its 1.4 Alpha u...
As much as we all probably dislike Maths as a subject, we do have to hand it to geometry for giving us the good old Hexgrid, home of some of the best strategy games. One such example, Price of Glory, has dropped its 1.4 Alpha update, stocked full... | Read more »
The SLC 2025 kicks off this month to cro...
Ever since the Solo Leveling: Arise Championship 2025 was announced, I have been looking forward to it. The promotional clip they released a month or two back showed crowds going absolutely nuts for the previous competitions, so imagine the... | Read more »
Dive into some early Magicpunk fun as Cr...
Excellent news for fans of steampunk and magic; the Precursor Test for Magicpunk MMORPG Crystal of Atlan opens today. This rather fancy way of saying beta test will remain open until March 5th and is available for PC - boo - and Android devices -... | Read more »
Prepare to get your mind melted as Evang...
If you are a fan of sci-fi shooters and incredibly weird, mind-bending anime series, then you are in for a treat, as Goddess of Victory: Nikke is gearing up for its second collaboration with Evangelion. We were also treated to an upcoming... | Read more »
Square Enix gives with one hand and slap...
We have something of a mixed bag coming over from Square Enix HQ today. Two of their mobile games are revelling in life with new events keeping them alive, whilst another has been thrown onto the ever-growing discard pile Square is building. I... | Read more »
Let the world burn as you have some fest...
It is time to leave the world burning once again as you take a much-needed break from that whole “hero” lark and enjoy some celebrations in Genshin Impact. Version 5.4, Moonlight Amidst Dreams, will see you in Inazuma to attend the Mikawa Flower... | Read more »
Full Moon Over the Abyssal Sea lands on...
Aether Gazer has announced its latest major update, and it is one of the loveliest event names I have ever heard. Full Moon Over the Abyssal Sea is an amazing name, and it comes loaded with two side stories, a new S-grade Modifier, and some fancy... | Read more »
Open your own eatery for all the forest...
Very important question; when you read the title Zoo Restaurant, do you also immediately think of running a restaurant in which you cook Zoo animals as the course? I will just assume yes. Anyway, come June 23rd we will all be able to start up our... | Read more »
Crystal of Atlan opens registration for...
Nuverse was prominently featured in the last month for all the wrong reasons with the USA TikTok debacle, but now it is putting all that behind it and preparing for the Crystal of Atlan beta test. Taking place between February 18th and March 5th,... | Read more »

Price Scanner via MacPrices.net

AT&T is offering a 65% discount on the ne...
AT&T is offering the new iPhone 16e for up to 65% off their monthly finance fee with 36-months of service. No trade-in is required. Discount is applied via monthly bill credits over the 36 month... Read more
Use this code to get a free iPhone 13 at Visi...
For a limited time, use code SWEETDEAL to get a free 128GB iPhone 13 Visible, Verizon’s low-cost wireless cell service, Visible. Deal is valid when you purchase the Visible+ annual plan. Free... Read more
M4 Mac minis on sale for $50-$80 off MSRP at...
B&H Photo has M4 Mac minis in stock and on sale right now for $50 to $80 off Apple’s MSRP, each including free 1-2 day shipping to most US addresses: – M4 Mac mini (16GB/256GB): $549, $50 off... Read more
Buy an iPhone 16 at Boost Mobile and get one...
Boost Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering one year of free Unlimited service with the purchase of any iPhone 16. Purchase the iPhone at standard MSRP, and then choose... Read more
Get an iPhone 15 for only $299 at Boost Mobil...
Boost Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering the 128GB iPhone 15 for $299.99 including service with their Unlimited Premium plan (50GB of premium data, $60/month), or $20... Read more
Unreal Mobile is offering $100 off any new iP...
Unreal Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering a $100 discount on any new iPhone with service. This includes new iPhone 16 models as well as iPhone 15, 14, 13, and SE... Read more
Apple drops prices on clearance iPhone 14 mod...
With today’s introduction of the new iPhone 16e, Apple has discontinued the iPhone 14, 14 Pro, and SE. In response, Apple has dropped prices on unlocked, Certified Refurbished, iPhone 14 models to a... Read more
B&H has 16-inch M4 Max MacBook Pros on sa...
B&H Photo is offering a $360-$410 discount on new 16-inch MacBook Pros with M4 Max CPUs right now. B&H offers free 1-2 day shipping to most US addresses: – 16″ M4 Max MacBook Pro (36GB/1TB/... Read more
Amazon is offering a $100 discount on the M4...
Amazon has the M4 Pro Mac mini discounted $100 off MSRP right now. Shipping is free. Their price is the lowest currently available for this popular mini: – Mac mini M4 Pro (24GB/512GB): $1299, $100... Read more
B&H continues to offer $150-$220 discount...
B&H Photo has 14-inch M4 MacBook Pros on sale for $150-$220 off MSRP. B&H offers free 1-2 day shipping to most US addresses: – 14″ M4 MacBook Pro (16GB/512GB): $1449, $150 off MSRP – 14″ M4... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.