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Description

A lightweight dependency injection framework for Objective-C. With support for iOS and MacOS X.

Why Objection?

  • "Annotation" Based Dependency Injection
  • Support for singletons
  • Lazy Instantiation over Eager Instantiation
  • Support for integrating external dependencies

Synopsis

Basic Usage

A class can be registered with objection using the macros objection_register or objection_register_singleton. The objection_requires macro can be used to declare what dependencies objection should provide to all instances it creates of that class. objection_requires can be used safely with inheritance.

Example

  @class Engine, Brakes;

  @interface Car : NSObject
  {
    Engine *engine;
    Brakes *brakes;
    BOOL awake;  
  }

  // Will be filled in by objection
  @property(nonatomic, retain) Engine *engine;
  // Will be filled in by objection
  @property(nonatomic, retain) Brakes *brakes;
  @property(nonatomic) BOOL awake;

  @implementation Car
  objection_register(Car)
  objection_requires(@"engine", @"brakes")
  @synthesize engine, brakes, awake;
  @end

Fetching Objects from Objection

An object can be fetched from objection by creating an injector and then asking for an instance of a particular class or protocol. An injector manages its own object context. Which means that a singleton is per injector and is not necessarily a true singleton.

- (void)someMethod {
  ObjectionInjector *injector = [Objection createInjector];
  id car = [injector getObject:[Car class]];
}

A global injector can be registered with Objection which can be used throughout your application or library.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
  ObjectionInjector *injector = [Objection createInjector];
  [Objection setGlobalInjector:injector];
}

- (void)viewDidLoad {
  id myModel = [[Objection globalInjector] getObject:[MyModel class]];
}

Registering Instances

Objection supports associating an object outside the context of Objection by configuring an ObjectionModule. You can also mark registered [singleton] classes as eager singletons. Eager singletons will be instantiated during the creation of the injector rather than being lazily instantiated.

Example

  @interface MyAppModule : ObjectionModule {

  }
  @end

  @implementation MyAppModule
  - (void)configure {
    [self bind:[UIApplication sharedApplication] toClass:[UIApplication class]];
    [self bind:[UIApplication sharedApplication].delegate toProtocol:@protocol(UIApplicationDelegate)];
    [self registerEagerSingleton:[Car class]];
  }

  @end
  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
    ObjectionInjector *injector = [Objection createInjector:[[[MyAppModule alloc] init] autorelease]];
    [Objection setGlobalInjector:injector];
  }

Instance Creation Notification

If an object is interested in knowing when it has been fully instantiated by objection it can implement the method awakeFromObjection.

Example

  @implementation Car
  //...
  objection_register_singleton(Car)
    - (void)awakeFromObjection {
      awake = YES;
    }
  @end  

TODO

  • Diagram class initialization and its relationship with Objection

Installation

iOS

  1. git clone git://github.com/atomicobject/objection.git
  2. Open Objection.xcodeproj
  3. Select Objection-iPhone target
  4. Select Release Configuration
  5. Build
  6. Add -ObjC and -all_load to Other Link Flags in your project

Include framework

#import <Objection-iPhone/Objection.h>

MacOS X

  1. git clone git://github.com/atomicobject/objection.git
  2. Open Objection.xcodeproj
  3. Select Objection target
  4. Select Release Configuration.
  5. Build

Include framework

#import <Objection/Objection.h>

Requirements

  • MacOS X 10.6 +
  • iOS 3.0 +

Authors

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