Objection, 一个轻量级的Objective-C依赖注入框架

pod 'Objection', '1.6.1' # 依赖注入.

#import <Objection/Objection.h>

@class Engine, Brakes;

@interface Car : NSObject

// 将会通过依赖注入赋值.
@property(nonatomic, strong) Engine *engine;
// 将会通过依赖注入赋值.
@property(nonatomic, strong) Brakes *brakes;
@property(nonatomic) BOOL awake;

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

@implementation Car
objection_requires_sel(@selector(engine), @selector(brakes))
@synthesize engine, brakes, awake;
@end

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

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
  JSObjectionInjector *injector = [JSObjection createInjector];
  [JSObjection setDefaultInjector:injector];
}

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

@implementation JSTableModel
objection_requires(@"RESTClient")
- (void)awakeFromNib {
  [[JSObjection defaultInjector] injectDependencies:self];
}
@end

- (void)someMethod {
  JSObjectionInjector *injector = [JSObjection createInjector];
  id car = injector[[Car class]];
}

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

@interface RequestDispatcher
@property(nonatomic, strong) JSObjectFactory *objectFactory
@end

@implementation RequestDispatcher
objection_requires(@"objectFactory") 

- (void)dispatch:(NSDictionary *)params
{
  Request *request = [self.objectFactory getObject:[Request class]];
  request.params = params;
  [request send];
}
@end

@interface MyAppModule : JSObjectionModule {
  
}
@end

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

@end
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
  JSObjectionInjector *injector = [JSObjection createInjector:[[MyAppModule alloc] init]];
  [JSObjection setDefaultInjector:injector];
}

@protocol ExternalUtility
  - (void)doSomething;  //!< 注意此处,确实是`-`减号.通常是不支持让元类直接支持协议的.此处是以类本身作为对象,来取执行协议,而不是使用该类的某一个实例.
@end

@interface ExternalUtility
  + (void)doSomething;
@end

@implementation ExternalUtility
  + (void)doSomething {...}
@end

// Module Configuration
- (void)configure {
  [self bindMetaClass:[ExternalUtility class] toProtocol:@protocol(ExternalUtility)];    
}

@interface SomeClass
{
  ...
}
//  使用 'assign' 是因为一个元类不受通常的 retain/release声明周期限制.
// 它将会一直存在,直到应用程序终止(类初始化 -> 应用终止),不管运行时有多少指向它的对象引用.
// 
@property (nonatomic, assign) id<ExternalUtility> externalUtility
@end

@interface CarProvider : NSObject <JSObjectionProvider>
@end

@implementation CarProvider
- (id)provide:(JSObjectionInjector *)context arguments:(NSArray *)arguments {
  // 手动创建对象的代码
  return car;
}
@end

@implementation MyAppModule
- (void)configure {
    [self bindProvider:[[CarProvider alloc] init] toClass:[Car class]];
    [self bindBlock:^(JSObjectionInjector *context) {
      // 手动创建对象.
      return car;          
    } toClass:[Car class]];
}
@end

@implementation MyAppModule
- (void)configure {
    [self bindClass:[Singleton class] inScope:JSObjectionScopeNormal];
    [self bindClass:[Car class] inScope:JSObjectionScopeSingleton];
}
@end

@interface ShinyCar : NSObject
@property (nonatomic, strong) Headlight *leftHeadlight;
@property (nonatomic, strong) Headlight *rightHeadlight;
@end

@implementation ShinyCar
objection_register(ShinyCar)
objection_requires_names((@{@"LeftHeadlight":@"leftHeadlight", @"RightHeadlight":@"rightHeadlight"}))
@synthesize leftHeadlight, rightHeadlight;
@end

@implementation NamedModule

- (void)configure
{
    [self bind:[[Headlight alloc]init] toClass:[Headlight class] named:@"RightHeadlight"];
    [self bindClass:[HIDHeadlight class] toClass:[Headlight class] named:@"LeftHeadlight"];

}
@end

@implementation MyAppModule
- (void)configure {
  [self registerEagerSingleton:[Car class]];
}

@end

injector = [otherInjector withModule:[[Level18Module alloc] init]] 
                          withoutModuleOfType:[Level17Module class]];

@implementation ViewController
objection_initializer(initWithNibName:bundle:, @"ViewController")
@end

@implementation ConfigurableCar
objection_requires(@"engine", @"brakes")
objection_initializer(initWithMake:model:)

@synthesize make;
@synthesize model;

- (instancetype)initWithMake:(NSString *)make model:(NSString *)model {
  ...
}
@end

- (void)buildCar {
  ConfigurableCar *car = [self.objectFactory getObjectWithArgs:[ConfigurableCar class], @"VW", @"Passat", nil];
  NSLog(@"Make: %@ Model: %@", car.make, car.model);
}

@implementation Truck
objection_requires(@"engine", @"brakes")
objection_initializer(truckWithMake:model:)
+ (instancetype)truckWithMake:(NSString *) make model: (NSString *)model {
  ...
}
@end

@implementation ConfigurableCar
- (instancetype) initWithModel:(NSString *)model {
    //....
}
@end

- (void)buildCar {
  ConfigurableCar *car = [self.objectFactory getObject:[ConfigurableCar class], 
                                           initializer: @selector(initWithModel:) 
                                           withArgumentList:@[@"Passat"]];
}