ReactiveCocoa is so useful that I can’t stop using it

[[145435]]

Foreplay

I personally highly recommend ReactiveCocoa. It is like the Chinese Tai Chi. Tai Chi gives birth to two opposites, two opposites give birth to four images, four images give birth to eight trigrams, and eight trigrams give birth to all things. ReactiveCocoa is a highly abstract programming framework. It is really abstract. At first glance, you don't know what it is for. After you use it, you will find that with it, you can do whatever you want. Coding has never been so smooth.

I won’t explain the principles of ReactiveCocoa here, because things that cannot be explained clearly are called abstract. I won’t mention related concepts either. I just want to show you how happy I am using it.

Forty-eight Hands of Code

Observation value

Don't move. I'll know if you move.

 @weakify(self);
 [RACObserve(self, value) subscribeNext:^(NSString* x) {
 @strongify(self);
 NSLog(@ "You moved" );
 }];

unilateral

You sing and I dance.

The content length of textField is mapped to a BOOL value and bound to the enable property of confirmButton. When the textField input content is not empty, confirmButton's enable = YES.

 RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "sing" ];
       [subscriber sendCompleted];
 return nil;
 }];
   RAC(self, value) = [signalA map:^id(NSString* value) {
 if ([value isEqualToString:@ "Singing" ]) {
 return @ "dance" ;
 }
 return @ "" ;
 }];

bilateral

If you go west, he goes east; if he goes left, you go right.

RACChannelTerminal *channelA = RACChannelTo(self, valueA);
 RACChannelTerminal *channelB = RACChannelTo(self, valueB);
 [[channelA map:^id(NSString *value) {
 if ([value isEqualToString:@ "西" ]) {
 return @ "East" ;
 }
 return value;
 }]subscribe:channelB];
 [[channelB map:^id(NSString *value) {
 if ([value isEqualToString:@ "left" ]) {
 return @ "right" ;
 }
 return value;
 }]subscribe:channelA];
 [[RACObserve(self, valueA) filter:^BOOL(id value) {
 return value ? YES : NO;
 }] subscribeNext:^(NSString* x) {
 NSLog(@ "You to %@" , x);
 }];
 [[RACObserve(self, valueB) filter:^BOOL(id value) {
 return value ? YES : NO;
 }] subscribeNext:^(NSString* x) {
 NSLog(@ "He said %@" , x);
 }];
 self.valueA = @ "西" ;
 self.valueB = @ "left" ;

 2015-08-15 20:14:46.544 Test[2440:99901] You go west
 2015-08-15 20:14:46.544 Test[2440:99901] He went east
 2015-08-15 20:14:46.545 Test[2440:99901] He turned left
 2015-08-15 20:14:46.545 Test[2440:99901] You turn right

acting

You are a programmer, please help me write an app.

 @protocol Programmer <NSObject>
 - ( void )makeAnApp;
 @end

 RACSignal *ProgrammerSignal =
 [self rac_signalForSelector:@selector(makeAnApp)
               fromProtocol:@protocol(Programmer)];
 [ProgrammerSignal subscribeNext:^(RACTuple* x) {
 NSLog(@ "It took a month to write the app" );
 }];
 [self makeAnApp];

 2015-08-15 20:46:45.720 Test[2817:114564] It took a month to write the app

broadcast

Knowing your channel, I can hear you.

 [[[NSNotificationCenter defaultCenter] rac_addObserverForName:@ "Code Channel" object:nil] subscribeNext:^(NSNotification* x) {
 NSLog(@ "skills: %@" , x.userInfo[@ "skills" ]);
 }];
 [[NSNotificationCenter defaultCenter] postNotificationName:@ "Code Channel" object:nil userInfo:@{@ "Skills" :@ "Write with care" }];

 2015-08-15 20:41:15.786 Test[2734:111505] Tips: Write carefully

connect

Life is one story after another.

 RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "I'm in love" ];
    [subscriber sendCompleted];
 return nil;
 }];
 RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "I'm getting married" ];
    [subscriber sendCompleted];
 return nil;
 }];
 [[signalA concat:signalB] subscribeNext:^(id x) {
 NSLog(@ "%@" ,x);
 }];

 2015-08-15 12:19:46.707 Test[1845:64122] I'm in love
 2015-08-15 12:19:46.707 Test[1845:64122] I'm married

merge

Sewage should flow into sewage treatment plants for treatment.

 RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "paper mill wastewater" ];
 return nil;
 }];
 RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "electroplating plant wastewater" ];
 return nil;
 }];
 [[RACSignal merge:@[signalA, signalB]] subscribeNext:^(id x) {
 NSLog(@ "Processing%@" , x);
 }];

 2015-08-15 12:10:05.371 Test[1770:60147] Treating paper mill wastewater
 2015-08-15 12:10:05.372 Test[1770:60147] Treatment of electroplating plant wastewater

combination

You are red and I am yellow, so we are red and yellow. You are white and I have not changed, so we are white and yellow.

 RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "red" ];
    [subscriber sendNext:@ "白" ];
 return nil;
 }];
 RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@ "白" ];
 return nil;
 }];
 [[RACSignal combineLatest:@[signalA, signalB]] subscribeNext:^(RACTuple* x) {
    RACTupleUnpack(NSString *stringA, NSString *stringB) = x;
 NSLog(@ "We are %@%@" , stringA, stringB);
 }];

 2015-08-15 12:14:19.837 Test[1808:62042] We are red and yellow
 2015-08-15 12:14:19.837 Test[1808:62042] We are white and yellow

compression

You are red and I am yellow, we are red and yellow, you are white, I haven't changed, oh, then wait until I change.

 RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 [subscriber sendNext:@ "red" ];
    [subscriber sendNext:@ "白" ];
 return nil;
 }];
 RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@ "白" ];
 return nil;
 }];
 [[signalA zipWith:signalB] subscribeNext:^(RACTuple* x) {
    RACTupleUnpack(NSString *stringA, NSString *stringB) = x;
 NSLog(@ "We are %@%@" , stringA, stringB);
 }];

 2015-08-15 20:34:24.274 Test[2660:108483] We are red and white

Mapping

I can turn stone into gold.

 RACSignal *signal = [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@ "石" ];
 return nil;
 }] map:^id(NSString* value) {
 if ([value isEqualToString:@ "石" ]) {
 return @ "gold" ;
 }
 return value;
 }];
 [signal subscribeNext:^(id x) {
 NSLog(@ "%@" , x);
 }];

 2015-08-16 20:00:12.853 Test[740:15871] Gold

Reduction

Sugar plus water turns into sugar water.

 RACSignal *sugarSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@ "sugar" ];
 return nil;
 }];
 RACSignal *waterSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@ "water" ];
 return nil;
 }];
 [[RACSignal combineLatest:@[sugarSignal, waterSignal] reduce:^id (NSString* sugar, NSString*water){
 return [sugar stringByAppendingString:water];
 }] subscribeNext:^(id x) {
 NSLog(@ "%@" , x);
 }];

 2015-08-16 20:07:00.356 Test[807:19177] Sugar water

filter

No entry for those under 18 years old.

 [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@(15)];
    [subscriber sendNext:@(17)];
    [subscriber sendNext:@(21)];
    [subscriber sendNext:@(14)];
    [subscriber sendNext:@(30)];
 return nil;
 }] filter:^BOOL(NSNumber* value) {
 return value.integerValue >= 18;
 }] subscribeNext:^(id x) {
 NSLog(@ "%@" , x);
 }];

 2015-08-16 20:11:20.071 Test[860:21214] 21
 2015-08-16 20:11:20.071 Test[860:21214] 30

Flat

Beat the eggs, fry the eggs and serve.

 [[[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "egg liquid" );
 [subscriber sendNext:@ "egg liquid" ];
    [subscriber sendCompleted];
 return nil;
 }] flattenMap:^RACStream *(NSString* value) {
 return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "Pour %@ into the pan and fry" ,value);
 [subscriber sendNext:@ "Fried Egg" ];
        [subscriber sendCompleted];
 return nil;
 }];
 }] flattenMap:^RACStream *(NSString* value) {
 return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "Put %@ on disk" , value);
 [subscriber sendNext:@ "serve" ];
        [subscriber sendCompleted];
 return nil;
 }];
 }] subscribeNext:^(id x) {
 NSLog(@ "%@" , x);
 }];

 2015-08-16 20:39:34.786 Test[1226:34386] Beat the egg
 2015-08-16 20:39:34.787 Test[1226:34386] Pour the egg liquid into the pan and fry
 2015-08-16 20:39:34.787 Test[1226:34386] Put the fried eggs on the plate
 2015-08-16 20:39:34.787 Test[1226:34386] Serving

order

It only takes three steps to stuff an elephant into the refrigerator: open the refrigerator door, stuff the elephant into the refrigerator, and close the refrigerator door.

 [[[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "Open refrigerator door" );
    [subscriber sendCompleted];
 return nil;
 }] then:^RACSignal *{
 return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "Put the elephant in the refrigerator" );
       [subscriber sendCompleted];
 return nil;
 }];
 }] then:^RACSignal *{
 return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "Close the refrigerator door" );
        [subscriber sendCompleted];
 return nil;
 }];
 }] subscribeCompleted:^{
 NSLog(@ "Put the elephant in the refrigerator" );
 }];

 2015-08-16 20:45:27.724 Test[1334:37870] Open the refrigerator door
 2015-08-16 20:45:27.725 Test[1334:37870] Stuff the elephant into the refrigerator
 2015-08-16 20:45:27.725 Test[1334:37870] Close the refrigerator door
 2015-08-16 20:45:27.726 Test[1334:37870] Stuffed the elephant into the refrigerator

Order

I command you to surrender immediately.

 RACCommand *aCommand = [[RACCommand alloc] initWithSignalBlock:^RACSignal *(id input) {
 return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "I surrender" );
       [subscriber sendCompleted];
 return nil;
 }];
 }];
 [aCommand execute:nil];

 2015-08-16 20:54:32.492 Test[1450:41849] I surrender

Delay

Wait for me, I'll be there in 10 seconds.

 [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "Wait for me, I'll be there in 10 seconds" );
    [subscriber sendNext:nil];
    [subscriber sendCompleted];
 return nil;
 }] delay:10] subscribeNext:^(id x) {
 NSLog(@ "I'm here" );
 }];

 2015-08-16 21:00:57.622 Test[1619:45924] Wait for me, I'll be there in 10 seconds
 2015-08-16 21:01:07.624 Test[1619:45924] I'm here

Replay

Make it once, watch it many times.

 RACSignal *replaySignal = [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "The famous director made a movie called "My Boyfriend is a Programmer"" );
 [subscriber sendNext:@ "《My Boyfriend is a Programmer》" ];
 return nil;
 }] replay];
 [replaySignal subscribeNext:^(id x) {
 NSLog(@ "Xiao Ming read %@" , x);
 }];
 [replaySignal subscribeNext:^(id x) {
 NSLog(@ "Xiaohong also watched %@" , x);
 }];

 2015-08-16 21:18:38.002 Test[1854:54712] A famous director made a movie called "My Boyfriend is a Programmer"
 2015-08-16 21:18:38.004 Test[1854:54712] Xiao Ming watched "My Boyfriend is a Programmer"
 2015-08-16 21:18:38.004 Test[1854:54712] Xiaohong also watched "My Boyfriend is a Programmer"

timing

Take this medicine every 8 hours.

 [[RACSignal interval:60*60*8 onScheduler:[RACScheduler mainThreadScheduler]] subscribeNext:^(id x) {
 NSLog(@ "Take medicine" );
 }];

time out

I've been waiting for you for an hour, and you haven't come yet, so I'm leaving.

 [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 NSLog(@ "I'm almost there" );
        [subscriber sendNext:nil];
        [subscriber sendCompleted];
 return nil;
    }] delay:60*70] subscribeNext:^(id x) {
        [subscriber sendNext:nil];
        [subscriber sendCompleted];
 }];
 return nil;
 }] timeout:60*60 onScheduler:[RACScheduler mainThreadScheduler]] subscribeError:^(NSError *error) {
 NSLog(@ "I've been waiting for you for an hour, but you haven't come yet, so I'm leaving" );
 }];

 2015-08-16 21:40:09.068 Test[2041:64720] I'm almost there
 2015-08-16 22:40:10.048 Test[2041:64720] I've been waiting for you for an hour, but you haven't come yet. I'm leaving.

Retry

It may take hundreds of failures before success.

 __block int failedCount = 0;
 [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
 if (failedCount < 100) {
 failedCount++;
 NSLog(@ "I failed" );
        [subscriber sendError:nil];
 } else {
 NSLog(@ "After hundreds of failures" );
        [subscriber sendNext:nil];
 }
 return nil;
 }] retry] subscribeNext:^(id x) {
 NSLog(@ "Finally succeeded" );
 }];

 2015-08-16 21:59:07.159 Test[2411:77080] I failed
 2015-08-16 21:59:07.159 Test[2411:77080] I failed
 2015-08-16 21:59:07.159 Test[2411:77080] I failed
 2015-08-16 21:59:07.159 Test[2411:77080] I failed
 2015-08-16 21:59:07.160 Test[2411:77080] I failed
 2015-08-16 21:59:07.160 Test[2411:77080] I failed
 2015-08-16 21:59:07.161 Test[2411:77080] I failed
 2015-08-16 21:59:07.162 Test[2411:77080] I failed
 ...
 2015-08-16 21:59:07.162 Test[2411:77080] I failed
 2015-08-16 21:59:07.163 Test[2411:77080] I failed
 2015-08-16 21:59:07.163 Test[2411:77080] I failed
 2015-08-16 21:59:07.163 Test[2411:77080] I failed
 2015-08-16 21:59:07.164 Test[2411:77080] I failed
 2015-08-16 21:59:07.164 Test[2411:77080] I failed
 2015-08-16 21:59:07.164 Test[2411:77080] I failed
 2015-08-16 21:59:07.165 Test[2411:77080] After hundreds of failures
 2015-08-16 21:59:07.165 Test[2411:77080] Finally succeeded

Throttling

Sorry, only one person can pass through here per second.

 [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [subscriber sendNext:@ "Passenger A" ];
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
 [subscriber sendNext:@ "Passenger B" ];
 });
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
 [subscriber sendNext:@ "Passenger C" ];
 [subscriber sendNext:@ "Passenger D" ];
        [subscriber sendNext:@ "Passenger E" ];
 });
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
 [subscriber sendNext:@ "Passenger F" ];
 });
 return nil;
 }] throttle:1] subscribeNext:^(id x) {
 NSLog(@ "%@ passed" , x);
 }];

 2015-08-16 22:08:45.677 Test[2618:83764] Passenger A
 2015-08-16 22:08:46.737 Test[2618:83764] Passenger B
 2015-08-16 22:08:47.822 Test[2618:83764] Passenger E
 2015-08-16 22:08:48.920 Test[2618:83764] Passenger F

condition

Until the end of the world can't separate us.

 [[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    [[RACSignal interval:1 onScheduler:[RACScheduler mainThreadScheduler]] subscribeNext:^(id x) {
 [subscriber sendNext:@ "Till the end of the world do us part" ];
 }];
 return nil;
 }] takeUntil:[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
 NSLog(@ "The end of the world is here" );
 [subscriber sendNext:@ "The end of the world is here" ];
 });
 return nil;
 }]] subscribeNext:^(id x) {
 NSLog(@ "%@" , x);
 }];

 2015-08-16 22:17:22.648 Test[2766:88737] Only the end of the world can separate us
 2015-08-16 22:17:23.648 Test[2766:88737] Only the end of the world can separate us
 2015-08-16 22:17:24.645 Test[2766:88737] Only the end of the world can separate us
 2015-08-16 22:17:25.648 Test[2766:88737] Only the end of the world can separate us
 2015-08-16 22:17:26.644 Test[2766:88737] Only the end of the world can separate us
 2015-08-16 22:17:26.645 Test[2766:88737] The end of the world has arrived

Finished

ReactiveCocoa is so elegant that once you use it, you can't stop. The above is just the tip of the iceberg. I hope I can arouse your interest.