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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Skype 7.37.0.178 - Voice-over-internet p...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
EtreCheck 3.0.5 - For troubleshooting yo...
EtreCheck is an app that displays the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to... Read more
Amadeus Pro 2.3.1 - Multitrack sound rec...
Amadeus Pro lets you use your Mac computer for any audio-related task, such as live audio recording, digitizing tapes and records, converting between a variety of sound formats, etc. Thanks to its... Read more
NeoFinder 6.9.3 - Catalog your external...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs all your data, so you stay in control of your data archive or disk... Read more
WhatsApp 0.2.1880 - Desktop client for W...
WhatsApp is the desktop client for WhatsApp Messenger, a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for... Read more
Hazel 4.0.6 - Create rules for organizin...
Hazel is your personal housekeeper, organizing and cleaning folders based on rules you define. Hazel can also manage your trash and uninstall your applications. Organize your files using a familiar... Read more
Apple iBooks Author 2.5 - Create and pub...
Apple iBooks Author helps you create and publish amazing Multi-Touch books for iPad. Now anyone can create stunning iBooks textbooks, cookbooks, history books, picture books, and more for iPad. All... Read more
MYStuff Pro 2.0.26 - $39.99
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more
MarsEdit 3.7.8 - Quick and convenient bl...
MarsEdit is a blog editor for OS X that makes editing your blog like writing email, with spell-checking, drafts, multiple windows, and even AppleScript support. It works with with most blog services... Read more
Yasu 3.0.3 - System maintenance app; per...
Yasu was created with System Administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks quickly within a... Read more

The new Clash of Kings is just for Weste...
If you’ve played the original Clash of Kings, you’ll probably recognise the city building, alliance forging and strategic battles in Clash of Kings: The West. What sets this version apart is that it’s tailor made for a Western audience and the... | Read more »
Frost - Survival card game (Games)
Frost - Survival card game 1.12.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.12.1 (iTunes) Description: *Warning: the game will work on iPhone 5C and above and iPad Pro / 4. Other devices are not supported* | Read more »
How to build and care for your team in D...
Before you hit the trail and become a dog sledding legend, there’s actually a fair bit of prep work to be done. In Dog Sled Saga, you’re not only racing, you’re also building and caring for a team of furry friends. There’s a lot to consider—... | Read more »
How to win every race in Dog Sled Saga
If I had to guess, I’d say Dog Sled Saga is the most adorable racing game on the App Store right now. It’s a dog sled racing sim full of adorable, loyal puppies. Just look at those fluffy little tails wagging. Behind that cute, pixelated facade is... | Read more »
Let the war games commence in Gunship Ba...
Buzz Lightyear famously said, “This isn’t flying, this is falling – with style!” In the case of Gunship Battle: Second War, though, this really is flying - with style! The flight simulator app from Joycity puts you in control of 20 faithfully... | Read more »
How to get a high score in Fired Up
Fired Up is Noodlecake Games’ high score chasing, firefighting adventure. You take control of a wayward firefighter who propels himself up the side of a highrise with blasts of water. Sound silly? It is. It’s also pretty difficult. You can’t... | Read more »
NBA 2K17 (Games)
NBA 2K17 1.0 Device: iOS iPhone Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: Following the record-breaking launch of NBA 2K16, the NBA 2K franchise continues to stake its claim as the most authentic sports video... | Read more »
Dog Sled Saga (Games)
Dog Sled Saga 1.0.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.1 (iTunes) Description: A game by Dan + Lisa As a rookie musher, foster a dogsledding team whose skills will grow if they're treated right. Week by... | Read more »
60 Seconds! Atomic Adventure (Games)
60 Seconds! Atomic Adventure 1.2 Device: iOS Universal Category: Games Price: $2.99, Version: 1.2 (iTunes) Description: 60 Seconds! is a dark comedy atomic adventure of scavenge and survival. Collect supplies and rescue your family... | Read more »
Tons of Bullets! (Games)
Tons of Bullets! 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Tons of BulletsA retro 2D pixel platformer infused with tons of bullets and tons of features!Fight as Kenji the Ninja and... | Read more »

Price Scanner via MacPrices.net

21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $120 off MSRP including free shipping plus NY sales tax only: - 21″ 3.1GHz iMac 4K: $1379 $120 off MSRP - 21″ 2.8GHz iMac: $1199.99 $100 off MSRP - 21″ 1... Read more
13-inch 2.7GHz/256GB Retina MacBook Pro on sa...
Amazon.com has the 13″ 2.7GHz/256GB Retina Apple MacBook Pro on sale for $151 off MSRP including free shipping: - 13″ 2.7GHz/256GB Retina MacBook Pro (sku MF840LL/A): $1348 $151 off MSRP Read more
Apple TVs on sale for up to $50 off MSRP
Best Buy has 32GB and 64GB Apple TVs on sale for $40-$50 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store... Read more
Apple refurbished 13-inch Retina MacBook Pros...
Apple has Certified Refurbished 13″ Retina MacBook Pros available for up to $270 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.7GHz... Read more
Duplicate Sweeper Free On Mac App Store For O...
To celebrate the launch of Apple’s latest macOS Sierra, Stafford, United Kingdom based Wide Angle Software has announced that its duplicate file finder software, Duplicate Sweeper, is now available... Read more
13-inch Retina MacBook Pros on sale for up to...
B&H Photo has 13″ Retina Apple MacBook Pros on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro: $1174.99 $125 off MSRP - 13... Read more
Evidence Surfaces Pointing To New A10X Chip F...
Citing a job description for a Project Lead position at Apple’s Austin, Texas engineering labs, Motley Fool’s Ashraf Eassa deduces that development is progressing well on Apple’s next-generation in-... Read more
Check Print’R for macOS Allows Anyone to Easi...
Delaware-based Match Software has announced the release and immediate availability of Check Print’R 3.21, an important update to their easy-to-use check printing application for macOS. Check Print’R... Read more
Apple refurbished 11-inch MacBook Airs availa...
Apple has Certified Refurbished 11″ MacBook Airs (the latest models), available for up to $170 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Apple refurbished 15-inch Retina MacBook Pros...
Apple has Certified Refurbished 2015 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2... Read more

Jobs Board

*Apple* Retail - Multiple Positions- Manhatt...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. *Apple* Mac Engineer - Net2Source Inc....
…staffing, training and technology. We have following position open with our client. Sr. Apple Mac Engineer6+ Months CTH Start date : 19th Sept Travelling Job If Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Restaurant Manager (Neighborhood Captain) - A...
…in every aspect of daily operation. WHY YOU'LL LIKE IT: You'll be the Big Apple . You'll solve problems. You'll get to show your ability to handle the stress and Read more
US- *Apple* Store Leader Program - Apple (Un...
…Summary Learn and grow as you explore the art of leadership at the Apple Store. You'll master our retail business inside and out through training, hands-on Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.