TweetFollow Us on Twitter

Dynamic Bundles Volume Number: 17 (2001)
Issue Number: 1
Column Tag: Mac OS X

Dynamic Bundles and Runtime Loading in OS X

By Andrew C. Stone

The Subtitle in Italics

As an application gets larger and more complex, the end user may perceive that the application loads slowly. Of course one can throw faster and multiple CPUs at the problem, but if you take advantage of dynamic bundle loading, your application can grow in functionality, but the time to launch remains lightning quick. How is this done? Simply by only loading the resources the user really needs at the moment. This article will show you how to architect your application to take advantage of bundles and late-loading.

Consider the fact that a typical application may have dozens of special panels and facilities that are occasionally accessed by the end user. There is no reason to load either the code or the resources for these panels until the end user actually requests that functionality.

There are many advantages to an application that dynamically loads bundles besides just fast launches. For example, in Stone Create, not only are all the inspectors, panels, and editors loaded on demand, but there is also a facility to load new tools at runtime. Any bundles found in the Tools directory are loaded and added to the tool palette when a new document is created. For example, the "Star" and "Embed" objects are loaded this way. New tools can be created and added without Create knowing anything about these in advance. By creating and adhering to protocols, which are sets of methods that must be implemented by an object, your application can deal with brand new objects at runtime.

The CFBundle, and its Cocoa cover class, NSBundle, handle all the details of locating and loading resources on demand. Most developers just use these for user interfaces, images, sounds and resource files, but it's simple to also load code on demand. The question then becomes, "how can I refer to code that is not yet loaded?" and "how can I compile code that has unresolved symbols"?

PreferencesController Bundle Example

One feature which makes OS X applications so powerful is the ease of user customization through the NSUserDefaults mechanism. Therefore, most applications require a user interface for preferences, but why load this panel and the code which controls it before it's absolutely needed if at all? We'll use the example of a preferences panel as a likely target for "bundling". The object "PreferenceController" is an NSWindowController subclass, which knows how to return a single instance of itself with a factory method, +sharedInstance:, because there is only one preferences panel in any application:

+ (id)sharedInstance {
    static PreferencesController *sharedPreferences = nil;

    // the first time through, we get the singleton preferences controller:
    if (!sharedPreferences) {
         sharedPreferences = [[PreferencesController                            allocWithZone:NULL] init];
    }

    return sharedPreferences;
}

Our dynamic loading code will assume that every bundle responds to "+ sharedInstance" if there are only one of these objects (for example, there is only one Color panel per application).

If PreferenceController is linked into the application, you would have a method to bring up the panel in your application delegate object:

- (IBAction)showPreferencesPanelAction:(id)sender {
   [[PreferenceController sharedInstance] showWindow:self];
}

but then, that code would be loaded at the launch of the application, because it has to be compiled into the application's binary since it is referenced by name. The way we move to a dynamicly loaded model is to never refer to this class, except in a string as an argument to our dyamic loading method sharedInstanceOfClassName:, which appears later in the article:

    [[self sharedInstanceOfClassName:@"PreferencesController"] showWindow:self];

Now, the code will compile without including the PreferencesController class. Our job is to be sure it gets loaded when first needed. Typically, I add the bundle loading code to the NSApplication's delegate, which can be globally accessed with:

[NSApp delegate]

Another strategy, and a topic of a later article, is to use categories, and add that functionality right to the NSBundle class. I prefer using the NSApp's delegate because you can add cover methods for loading panels in a single class, and then connect menu items to the instantiated application delegate in the application's main NIB file. So, in this example, we would:

  1. add a method to the NSApp delegate class:
    - (IBAction)showPreferencesPanelAction:(id)sender;
    
  2. In InterfaceBuilder, connect the menu item "Preferences..." to the app delegate target, with the action "showPreferencesPanelAction:". You can quickly add actions to IB by dragging in the .h or .m file from ProjectBuilder into the document window of your nib. This is equivalent to "Classes->Read File...".
  3. When that menu item gets triggered, the application delegate will load the needed code. Subsequent invocations of the panel will be even swifter, but loading a single panel and controller code is pretty fast anyway.

Bundle Integration in Project Builder

From a Project Builder standpoint, your application's project becomes an aggregate of targets: the application target, and a target for each of the dynamically loaded bundles. Your application should add the product of each bundle to the Copy Files phase in the "Files and Build Phases" tab of the application target inspector.


Figure 1. Copy files phase adds bundles to the application target.

For backwards compatibility with OpenStep, I use the "Resources" directory to store bundles. The following code assumes that you are putting your bundles into the Resources subdirectory in <YOUR_APP_NAME>.app/Contents/. You change where they are copied to with the "Where:" pop-up in the Files & Build Phases pane of the Target Inspector. It is probably more intuitive to place bundles in "Bundles" subdirectory, and if you do, change the pathForResource:ofType: call to pathForBundle:ofType: in the method -(id)instanceOfClassName:(NSString *)name shared:(BOOL)shared.

Before looking at the very simple dynamic loading code, there is one point to consider. A Cocoa bundle has the notion of a principal class. That is the class that is both the owner of the NIB file, and the class that needs to be accessed first when the bundle is loaded. Many times, a bundle will only have one class in it, but its a potential gotcha to not specify the principal class if there are more than one class in the bundle. You assign the principal class in Project Builder - click the bundle target to load the target inspector. Select the "Bundle Settings" tab, and under the "Cocoa Specific" settings, type in the name of the class in the Principal class field, in this example, PreferencesController. Other fields let you assign version information, help files, main nib files, but these are optional.

The Dynamic Loading Code

The code offers two types of dynamic code loading - both singleton class instances such as the PreferencesController with sharedInstanceOfClassName, as well as simple new instances for each invocation with instanceOfClassName. Both use the same core code with a "shared" flag:

- (id)sharedInstanceOfClassName:(NSString *)name
{
    return [self instanceOfClassName:name shared:YES];
}

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

instanceOfClassName would be used, for example, in a document-based architecture application where each document had its own version of that bundle's nib. An example would be a sheet that gets run on a per-document basis - because more than one document can be in a sheet-modal state at the same time. In this case, the document becomes responsible for freeing the bundle resources upon closing. Singleton instances are not freed until the application quits.

- (id)instanceOfClassName:(NSString *)name shared:(BOOL)shared
{
    id obj = nil;
    // NSBundle does the work of finding the bundle
    // pathForResource means "look into Resources folder"
    // use pathForBundle if you store them in the "Bundles" folder
    NSString *path = [[NSBundle mainBundle] 
                              pathForResource:name ofType:@"bundle"];
    if (path) {
        NSBundle *b = [[NSBundle allocWithZone:NULL] 
                                                   initWithPath:path];

        // the object we wish to return is an instance of the principal class:
        if ((b != nil) && ([b principalClass] !=NULL)) {

      // we either grab the sharedInstance or create a new one:
      if (shared) obj = [[b principalClass] sharedInstance];
      else obj = [[[b principalClass] allocWithZone:NULL] init];

    // provide Developer feedback if something has gone wrong:
        }  else NSLog(@"Can't Load %@!\n", path);
    } else NSLog(@"Couldn't find %@ bundle!\n",name);

    return obj;
}

Conclusion

When designing your application, it is good practice to decompose your functionality into small, loadable pieces. By using dynamically loaded bundles, you gain launch speed and can take advantage of runtime binding for loading new tools. Probably most importantly, bundles create a firm foundation for future feature growth without application bloat as well as provide a natural modularity that is easy to comprehend.


Andrew Stone <andrew@stone.com> is CEO of www.stone.com and has been working with Cocoa since 1989 with its introduction as NeXTStep.

 
AAPL
$102.99
Apple Inc.
+0.52
MSFT
$44.38
Microsoft Corpora
-0.50
GOOG
$532.71
Google Inc.
+6.17

MacTech Search:
Community Search:

Software Updates via MacUpdate

Evernote 5.6.2 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
OmniOutliner 4.1.3 - Organize your ideas...
OmniOutliner is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
BBEdit 11.0 - Powerful text and HTML edi...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
Apple Security Update 2014-005 - For OS...
Apple Security Update is recommended for all users and improves the security of Mac OS X. For information on the security content of this update, please visit this website: http://support.apple.com/... Read more
EyeTV 3.6.6 - Watch and record TV on you...
EyeTV brings a rich TV experience to your Mac. Watch live TV on your Mac. Pause, rewind, and record whenever you want. EyeTV gives you powerful control over what you watch and how you watch it. Put... Read more
RapidWeaver 6.0 - Create template-based...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
NTFS 12.0.39 - Provides full read and wr...
Paragon NTFS breaks down the barriers between Windows and OS X. Paragon NTFS effectively solves the communication problems between the Mac system and NTFS, providing full read and write access to... Read more
RestoreMeNot 2.0.3 - Disable window rest...
RestoreMeNot provides a simple way to disable the window restoration for individual applications so that you can fine-tune this behavior to suit your needs. Please note that RestoreMeNot is designed... Read more
Command-C 1.1.5 - Clipboard sharing tool...
Command-C is a revolutionary app which makes easy to share your clipboard between iOS and OS X using your local WiFi network, even if the app is not currently opened. Copy anything (text, pictures,... Read more
Macgo Blu-ray Player 2.10.9.1750 - Blu-r...
Macgo Mac Blu-ray Player can bring you the most unforgettable Blu-ray experience on your Mac. Overview Macgo Mac Blu-ray Player can satisfy just about every need you could possibly have in a Blu-ray... Read more

Latest Forum Discussions

See All

Worldly (Games)
Worldly 1.2 Device: iOS Universal Category: Games Price: $2.99, Version: 1.2 (iTunes) Description: | Read more »
Pro Strategy Football 2014 (Games)
Pro Strategy Football 2014 2014.141001 Device: iOS Universal Category: Games Price: $4.99, Version: 2014.141001 (iTunes) Description: Take the proven strategy of the PSF franchise and add in Casual Play, improved graphics and... | Read more »
Super Glyph Quest (Games)
Super Glyph Quest 1.01 Device: iOS Universal Category: Games Price: $2.99, Version: 1.01 (iTunes) Description: Adventure is back Questers! Combine elemental glyphs together to cast powerful spells and vanquish adorable monsters in... | Read more »
Fighting Fantasy: Caverns of the Snow Wi...
Fighting Fantasy: Caverns of the Snow Witch 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: Travel to Northern Allansia’s perilous Icefinger Mountains to defeat the wicked Snow Witch in this... | Read more »
Star Warfare 2: Payback Review
Star Warfare 2: Payback Review By Blake Grundman on October 22nd, 2014 Our Rating: :: ONE-TRICK PONYUniversal App - Designed for iPhone and iPad Unfortunately, it doesn’t take long for Star Warfare 2’s free-firing fun to turn into... | Read more »
TinType by Hipstamatic (Photography)
TinType by Hipstamatic 1.0 Device: iOS iPhone Category: Photography Price: $.99, Version: 1.0 (iTunes) Description: Create hauntingly beautiful, soul capturing portraits with TinType by Hipstamatic. Inspired by daguerreotypes,... | Read more »
The Latest Update for Heroes of Dragon A...
The Latest Update for Heroes of Dragon Age Introduces Daily PvE Challenges Posted by Ellis Spice on October 22nd, 2014 [ permalink ] | Read more »
Bee Brilliant Review
Bee Brilliant Review By Jennifer Allen on October 22nd, 2014 Our Rating: :: SAMEY MATCH-3Universal App - Designed for iPhone and iPad Want even more Match-3 gaming and fancy a bee based twist? Bee Brilliant is that game. Don’t... | Read more »
A New Trailer has Been Revealed for Epic...
A New Trailer has Been Revealed for Epic of Kings Posted by Jessica Fisher on October 22nd, 2014 [ permalink ] Dead Mage Inc. has released a new, action-packed trailer for the upcoming Epic of Kings. | Read more »
Find the Line Review
Find the Line Review By Campbell Bird on October 22nd, 2014 Our Rating: :: INSLIDE THE LINESUniversal App - Designed for iPhone and iPad Tease out beautiful line drawings in this unique, free-to-play puzzle game.   | Read more »

Price Scanner via MacPrices.net

Save with Best Buy’s College Student Deals
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through November 1st. Anyone with a valid .EDU email address can take advantage... Read more
iPad Air 2 & iPad mini 3 Best Tablets Yet...
The new iPads turned out to be pretty much everything I’d been hoping for and more than I’d expected.”More” particularly in terms of a drinking-from-a-firehose choice of models and configurations,... Read more
Drafts 4 Reinvents iOS Productivity App
N Richland Hills, Texas based Agile Tortoise has announced the release of Drafts 4 for iPhone and iPad. Drafts is a quick capture note taking app with flexible output actions. Drafts 4 scales from... Read more
AT&T accepting preorders for new iPads fo...
AT&T Wireless is accepting preorders for the new iPad Air 2 and iPad mini 3, cellular models, for $100 off MSRP with a 2-year service agreement: - 16GB iPad Air 2 WiFi + Cellular: $529.99 - 64GB... Read more
Apple offering refurbished Mac Pros for up to...
The Apple Store is offering Apple Certified Refurbished 2013 Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Select MacBook Airs $100 off MSRP, free shipp...
B&H Photo has 2014 a couple of MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels Desktop and LoJack for... Read more
13-inch 2.5GHz MacBook Pro on sale for $100 o...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Strong iPhone, Mac And App Store Sales Drive...
Apple on Monday announced financial results for its fiscal 2014 fourth quarter ended September 27, 2014. The Company posted quarterly revenue of $42.1 billion and quarterly net profit of $8.5 billion... Read more
Apple Posts How-To For OS X Recovery
OS X 10.7 Lion and later include OS X Recovery. This feature includes all of the tools you need to reinstall OS X, repair your disk, and even restore from a Time Machine backup. OS X Recovery... Read more
Mac OS X Versions (Builds) Supported By Vario...
Apple Support has posted a handy resource explaining which Mac OS X versions (builds) originally shipped with or are available for your computer via retail discs, downloads, or Software Update. Apple... Read more

Jobs Board

Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.