WKInterfaceController+Reactive

WKInterfaceController+Reactive.h

@import WatchKit;
#import <ReactiveCocoa/ReactiveCocoa.h>

@interface WKInterfaceController (Reactive)

@property (nonatomic, readonly) RACSignal *activatedSignal;
@property (nonatomic, readonly) RACSignal *deactivatedSignal;
@property (nonatomic, readonly) RACSignal *didPresentControllerSignal;
@property (nonatomic, readonly) RACSignal *didPushControllerSignal;

/// Returns a signal that sends YES until the next time this interface is activated, then sends NO and completes.
/// One potential use for this would be to enable/disable a command for a sub interface that pops that interface
/// off the stack ONLY if the parent hasn't been shown again (like for Due Date changes, Comments, etc).
- (RACSignal *)yesUntilNextActivationSignal;

@end

WKInterfaceController+Reactive.m

#import "WKInterfaceController+Reactive.h"
#import <objc/runtime.h>

@interface WKInterfaceController (Reactive_Private)

@property (nonatomic, strong, readonly) RACSignal *activationSignal;

@end

@implementation WKInterfaceController (Reactive)

- (RACSignal *)activationSignal {
    void* activationSignalKey = &activationSignalKey;
    RACSignal *signal =  objc_getAssociatedObject(self, activationSignalKey);
    
    if (!signal) {
        signal = [RACSignal merge:@[[[self rac_signalForSelector:@selector(willActivate)] mapReplace:@YES],
                                    [[self rac_signalForSelector:@selector(didDeactivate)] mapReplace:@NO]]];
        objc_setAssociatedObject(self, activationSignalKey, signal, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    
    return signal;
}

- (RACSignal *)activatedSignal {
    return [self.activationSignal ignore:@NO];
}

- (RACSignal *)deactivatedSignal {
    return [self.activationSignal ignore:@YES];
}

- (RACSignal *)didPresentControllerSignal {
    return [self rac_signalForSelector:@selector(presentControllerWithName:context:)];
}

- (RACSignal *)didPushControllerSignal {
    return [self rac_signalForSelector:@selector(pushControllerWithName:context:)];
}

- (RACSignal *)yesUntilNextActivationSignal {
    return [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [subscriber sendNext:@YES];
        return nil;
    }] takeUntil:self.activatedSignal] concat:[RACSignal return:@NO]];
}

@end

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