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

Maya 2016 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
RapidWeaver 6.2.3 - Create template-base...
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
MacFamilyTree 7.5.2 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Paragraphs 1.0.1 - Writing tool just for...
Paragraphs is an app just for writers. It was built for one thing and one thing only: writing. It gives you everything you need to create brilliant prose and does away with the rest. Everything in... Read more
BlueStacks App Player 0.9.21 - Run Andro...
BlueStacks App Player lets you run your Android apps fast and fullscreen on your Mac. Version 0.9.21: Note: Now requires OS X 10.8 or later running on a 64-bit Intel processor. Initial stable... Read more
Tweetbot 2.0.2 - Popular Twitter client....
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Apple iBooks Author 2.3 - 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
NeoOffice 2014.12 - Mac-tailored, OpenOf...
NeoOffice is a complete office suite for OS X. With NeoOffice, users can view, edit, and save OpenOffice documents, PDF files, and most Microsoft Word, Excel, and PowerPoint documents. NeoOffice 3.x... Read more
Apple iTunes 12.2 - Play Apple Music...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Apple Security Update 2015-005 - For OS...
Apple Security Update 2015-005 is recommended for all users and improves the security of OS X. For detailed information about the security content of this update, please visit: http://support.apple.... Read more

Rage of Bahamut is Giving Almost All of...
The App Store isn't what it used to be back in 2012, so it's not unexpected to see some games changing their structures with the times. Now we can add Rage of Bahamut to that list with the recent announcement that the game is severely cutting back... | Read more »
Adventures of Pip (Games)
Adventures of Pip 1.0 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: ** ONE WEEK ONLY — 66% OFF! *** “Adventures of Pip is a delightful little platformer full of charm, challenge and impeccable... | Read more »
Divide By Sheep - Tips, Tricks, and Stre...
Who would have thought splitting up sheep could be so involved? Anyone who’s played Divide by Sheep, that’s who! While we’re not about to give you complete solutions to everything (because that’s just cheating), we will happily give you some... | Read more »
NaturalMotion and Zynga Have Started Tea...
An official sequel to 2012's CSR Racing is officially on the way, with Zynga and NaturalMotion releasing a short teaser trailer to get everyone excited. Well, as excited as one can get from a trailer with no gameplay footage, anyway. [Read more] | Read more »
Grab a Friend and Pick up Overkill 3, Be...
Overkill 3 is a pretty enjoyable third-person shooter that was sort of begging for some online multiplayer. Fortunately the begging can stop, because its newest update has added an online co-op mode. [Read more] | Read more »
Scanner Pro's Newest Update Adds Au...
Scanner Pro is one of the most popular document scanning apps on iOS, thanks in no small part to its near-constant updates, I'm sure. Now we're up to update number six, and it adds some pretty handy new features. [Read more] | Read more »
Heroki (Games)
Heroki 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: CLEAR THE SKIES FOR A NEW HERO!The peaceful sky village of Levantia is in danger! The dastardly Dr. N. Forchin and his accomplice,... | Read more »
Wars of the Roses (Games)
Wars of the Roses 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
TapMon Battle (Games)
TapMon Battle 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: It's time to battle!Tap! Tap! Tap! Try tap a egg to hatch a Tapmon!Do a battle with another tapmons using your hatched tapmons! *... | Read more »
Alchemic Dungeons (Games)
Alchemic Dungeons 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: ### Release Event! ### 2.99$->0.99$ for limited time! ### Roguelike Role Playing Game! ### Alchemic Dungeons is roguelike... | Read more »

Price Scanner via MacPrices.net

15-inch 2.5GHz Retina MacBook Pro on sale for...
Amazon.com has the 15″ 2.5GHz Retina MacBook Pro on sale for $2274 including free shipping. Their price is $225 off MSRP, and it’s the lowest price available for this model. Read more
Logo Pop Free Vector Logo Design App For OS X...
128bit Technologies has released of Logo Pop Free 1.2 for Mac OS X, a vector based, full-fledged, logo design app available exclusively on the Mac App Store for the agreeable price of absolutely free... Read more
21-inch 1.4GHz iMac on sale for $999, save $1...
B&H Photo has new 21″ 1.4GHz iMac on sale for $999 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Best Buy has the 21″ 1.4GHz iMac on sale for $999.99 on their... Read more
16GB iPad mini 3 on sale for $339, save $60
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $339 including free shipping plus NY tax only. Their price is $60 off MSRP. Read more
Save up to $40 on iPad Air 2, NY tax only, fr...
B&H Photo has iPad Air 2s on sale for up to $40 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $489 $10 off - 64GB iPad Air 2 WiFi: $559 $40 off - 128GB iPad Air... Read more
Apple Releases OS X 10.10.4 With WIFi Fix, iO...
On Tuesday, Apple released final versions of OS X 10.10.4 and iOS 8.4, as well as updates for the Safari browser for OS X Yosemite, Mavericks, and Mountain Lion. The OS X 10.10.4 update focuses on... Read more
Dual-Band High-Gain Antennas for Home Wi-Fi N...
Linksys has announced what it claims are the first dual-band, omni-directional high-gain antennas for the consumer market. The new Linksys high-gain antennas available in a 2- and 4-pack (WRT004ANT... Read more
Apple refurbished 2014 15-inch Retina MacBook...
The Apple Store has Apple Certified Refurbished 2014 15″ 2.2GHz Retina MacBook Pros available for $1609, $390 off original MSRP. Apple’s one-year warranty is included, and shipping is free. They have... Read more
Clearance 2014 MacBook Airs available for up...
Adorama has 2014 MacBook Airs on sale for up to $301 off original MSRP including NY + NJ sales tax and free shipping: - 11″ 256GB MacBook Air: $798 $301 off original MSRP - 13″ 128GB MacBook Air: $... Read more
5K iMacs on sale for $100 off MSRP, free ship...
B&H Photo has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 including free shipping plus NY tax only. Their price is $100 off MSRP. They have the 27″ 3.5GHz 5K iMac on sale for $2199, also $100... Read more

Jobs Board

*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Fulfillment Operations Execution Ana...
**Job Summary** The AMR Apple Fulfillment Operations Team is seeking a talented team player to drive the Apple Online Store (AOS) fulfillment performance to ensure a Read more
Localization Producer - *Apple* HR and Reta...
…project manager to support the Retail Globalization team. You will participate in Apple exponential inte ational growth and drive global project initiatives for the Read more
*Apple* Online Store UAT Lead - Apple (Unite...
**Job Summary** The Apple Online Store is a fast paced and ever evolving business environment. A UAT lead in this organization is able to have a direct impact on one of Read more
Senior Payments Security Manager - *Apple*...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments security manager to join the Apple Pay security team. You will Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.