Multicast Delegation

NSLondon January 2014 PechaKucha

1. MULTICAST
 DELEGATION @luka_bernardi
2. Communication Patterns Direct method invocations Notifications Delegates Block callbacks KVO Target-Action
3. Delegate
5. - (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated { ... }
6. Encapsulate Clustering Behaviour
7. Clustering Delegate View Controller mapView:regionDidChangeAnimated: mapView:regionDidChangeAnimated:
8. Clustering Delegate View Controller Proxy
9. NSProxy
10. @interface LBDelegateMatrioska () @property (nonatomic, strong) NSPointerArray *mutableDelegates; @end ! ! @implementation LBDelegateMatrioska ! - (instancetype)initWithDelegates:(NSArray *)delegates { _mutableDelegates = [NSPointerArray weakObjectsPointerArray]; [delegates enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { [_mutableDelegates addPointer:(void *)obj]; }]; return self; }
11. @interface LBRViewController () @property (weak, nonatomic) IBOutlet MKMapView *mapView; @property (strong, nonatomic) LBDelegateMatrioska *delegateMatrioska; @property (strong, nonatomic) LBClusteredMapViewDelegate *clusteringDelegate; @end ! @implementation LBRViewController ! - (void)viewDidLoad { [super viewDidLoad]; ! self.delegateMatrioska = ({ self.clusteringDelegate = [LBClusteredMapViewDelegate new]; NSArray *delegates = @[self.clusteringDelegate, self]; LBDelegateMatrioska *matrioska = [[LBDelegateMatrioska alloc] initWithDelegates:delegates]; matrioska; }); self.mapView.delegate = (id<MKMapViewDelegate>)self.delegateMatrioska; }
12. @implementation LBDelegateMatrioska ! ! #pragma mark - NSObject ! - (BOOL)respondsToSelector:(SEL)aSelector { id firstResponder = [self p_firstResponderToSelector:aSelector]; return (firstResponder ? YES : NO); }
13. @implementation LBDelegateMatrioska ! #pragma mark - NSProxy ! - (void)forwardInvocation:(NSInvocation *)invocation { for (id delegate in self.mutableDelegates) { if ([delegate respondsToSelector:invocation.selector]) { [invocation invokeWithTarget:delegate]; } } } ! - (NSMethodSignature *)methodSignatureForSelector:(SEL)sel { id firstResponder = [self p_firstResponderToSelector:sel]; if (firstResponder) { return [firstResponder methodSignatureForSelector:sel]; } return nil; }
14. #pragma mark - NSProxy ! - (void)forwardInvocation:(NSInvocation *)invocation { // If the invoked method return void I can safely call all the delegates // otherwise I just invoke it on the first delegate that // respond to the given selector if ([invocation methodReturnTypeIsVoid]) { for (id delegate in self.mutableDelegates) { if ([delegate respondsToSelector:invocation.selector]) { [invocation invokeWithTarget:delegate]; } } } else { id firstResponder = [self p_firstResponderToSelector:invocation.selector]; [invocation invokeWithTarget:firstResponder]; } }
15. context(@"when a method is called", ^{ it(@"should be received by all the delegates that receive the message", ^{ SEL testSelector = @selector(didSelect); #pragma clang diagnostic push #pragma clang diagnostic ignored "-Warc-performSelector-leaks" [[firstObject should] receive:testSelector]; [[secondObject should] receive:testSelector]; [[thirdObject shouldNot] receive:testSelector]; [(id <CannedProtocol>)matrioska performSelector:testSelector]; testSelector = @selector(didDeselect); [[firstObject shouldNot] receive:testSelector]; [[secondObject shouldNot] receive:testSelector]; [[thirdObject should] receive:testSelector]; [(id <CannedProtocol>)matrioska performSelector:testSelector]; #pragma clang diagnostic pop }); }); #import <Kiwi/NSProxy+KiwiVerifierAdditions.h>
16. Delegate Code Reuse
17. Think of it as a plugin
18. Use it to broadcast message with a contract Via @pedrogomes
19. Performance 15x Slower NSInvocation Allocation
20. Thanks! @luka_bernardi https://github.com/lukabernardi/LBDelegateMatrioska