前言

最近歌懒，ReactiveCocoa火的不行，網(wǎng)上各種大牛各種說RAC的優(yōu)點溯壶，早就有學習的想法及皂，一直沒有付諸行動，最近公司開發(fā)不是很緊張且改，特意學習了一下RAC验烧，以便以后改版使用。

1.[-subscribe…][RACSignal]該方法會檢測RACSignal中當前和以后的值又跛，來執(zhí)行subscribe中相應的方法碍拆。

example:

RACSignal *letters = [@“a b c d e f” componentsSeparatedByString:@“ “].rac_sequence.signal;

//數(shù)組中的元素分割成多個信號

[letters subscribeNext:^(id x){

NSLog(@“%@“, x);

}];

//letters信號的subscriber在signal的值改變時執(zhí)行相應方法

output:a b c d e f(每一行輸出一個字母)

2.[-subscribe…][RACSignal]

__block unsigned subscriptions =0;RACSignal *loggingSignal = [RACSignal createSignal:^ RACDisposable * (id subscriber) {? ? subscriptions++;? ? [subscriber sendCompleted];returnnil;}];

// Outputs:// subscription 1[loggingSignal subscribeCompleted:^{NSLog(@"subscription %u", subscriptions);}];// Outputs:// subscription 2[loggingSignal subscribeCompleted:^{NSLog(@"subscription %u", subscriptions);}];

執(zhí)行順序：創(chuàng)建RACSignal ->執(zhí)行subscribeCompleted->回調(diào)createSignal中的方法-執(zhí)行[subscriber sendCompleted]->回調(diào)[loggingSignal subscribeCompleted:]中的方法

總結(jié)：[RACSignal subscribeCompleted:]? [RACSignal subscribeNext:]都會回調(diào)createSignl中的block中的方法，但是block中的[sendCompleted] [sendNext]只會執(zhí)行他回調(diào)的方法慨蓝，即誰回調(diào)執(zhí)行誰感混。 但是，[doNext]和[doCompleted]中的block會執(zhí)行礼烈。

3.[-do…][RACSignal+Operations] ([doNext:][RACSignal] ? [doCompleted:][RACSignal])

__blockunsignedsubscriptions =0;RACSignal *loggingSignal = [RACSignal createSignal:^ RACDisposable * (id subscriber) {? ? subscriptions++;? ? [subscriber sendCompleted];returnnil;}];// Does not output anything yetloggingSignal = [loggingSignal doCompleted:^{NSLog(@"about to complete subscription %u", subscriptions);}];// Outputs:// about to complete subscription 1// subscription 1[loggingSignal subscribeCompleted:^{NSLog(@"subscription %u", subscriptions);}];

執(zhí)行doCompleted或者doNext時弧满，必須返回RACSignal,否則，不會執(zhí)行其block济丘。[doNext:][doCompleted]不會像[subscribeCompleted:][subscribeNext:]那樣主動去回調(diào)[createSignal:][RACSignal]中的block,而是谱秽，當[subscribe doNext:][subscribe doComplete]時執(zhí)行相應的動作洽蛀。

4.[-map:][RACStream]

map:映射的意思摹迷，此方法可以將一個信號映射成一個新的任意類型的信號。

RACSequence *letters = [@"A B C D E F G H I"componentsSeparatedByString:@" "].rac_sequence;// Contains: AA BB CC DD EE FF GG HH IIRACSequence *mapped = [letters map:^(NSString *value) {return[valuestringByAppendingString:value];}];

RACSequence *mapped2 = [letters map:(^NSString *value){

return @([value isEqualToString:@“a”]);

}];

如上郊供，可以將原來的letters信號串map成@“AA BB CC DD EE FF GG HH II”信號串峡碉，也可以map成BOOL類型的信號串

5.[-filter:][RACStream]

篩選符合條件的信號，組成一個只包含符合條件信號的信號流驮审。

RACSequence *numbers = [@"1 2 3 4 5 6 7 8 9"componentsSeparatedByString:@" "].rac_sequence;// Contains: 2 4 6 8RACSequence *filtered = [numbers filter:^ BOOL (NSString *value) {return(value.intValue %2) ==0;}];

如圖鲫寄，過濾出符合條件的signal吉执；

6.[-concat:][RACStream]

將一個信號流添加到另一個信號流后面。

RACSequence*letters= [@"A B C D E F G H I" componentsSeparatedByString:@""].rac_sequence;RACSequence*numbers= [@"123456789" componentsSeparatedByString:@""].rac_sequence;//Contains: A B C D E F G H I123456789RACSequence*concatenated= [letters concat:numbers];

7.[-flatten][RACStream]

(1)將兩個sequence合成一個sequence地来，其實質(zhì)就是concatenated戳玫。

RACSequence*letters= [@"A B C D E F G H I" componentsSeparatedByString:@""].rac_sequence;RACSequence*numbers= [@"123456789" componentsSeparatedByString:@""].rac_sequence;RACSequence*sequenceOfSequences=@[letters, numbers ].rac_sequence;//Contains: A B C D E F G H I123456789RACSequence*flattened= [sequenceOfSequences flatten];

（2）將兩個signal合成一個signal，其實質(zhì)就是merge未斑。

RACSubject*letters= [RACSubject subject];RACSubject*numbers= [RACSubject subject];RACSignal*signalOfSignals= [RACSignal createSignal:^ RACDisposable * (id subscriber) {? ? [subscriber sendNext:letters];[subscriber sendNext:numbers];[subscriber sendCompleted];returnnil;}];RACSignal*flattened= [signalOfSignals flatten];//Outputs: A1B C2[flattened subscribeNext:^(NSString*x) {? ? NSLog(@"%@",x);}];[letters sendNext:@"A"];[numbers sendNext:@"1"];[letters sendNext:@"B"];[letters sendNext:@"C"];[numbers sendNext:@"2"];

調(diào)用順序：createSignal->[flattend subscribeNext:]->[createSignal (^block)]->[letters sendNext:]->[flattend subscribeNext:^block]…(之后重復咕宿，sendNext之后，回調(diào)subscribeNext)蜡秽；

8.[-flattenMap:][RACStream]

實質(zhì)：mapping和flattening

RACSequence*numbers= [@"123456789" componentsSeparatedByString:@""].rac_sequence;//Contains:112233445566778899RACSequence*extended= [numbers flattenMap:^(NSString*num) {return@[num, num ].rac_sequence;}];//Contains:1_3_5_7_9_RACSequence*edited= [numbers flattenMap:^(NSString*num) {if(num.intValue %2==0) {return[RACSequence empty];? ? }else{? ? ? ? NSString*newNum= [num stringByAppendingString:@"_"];

return [RACSequence return:newNum];

}

}];

9.[-then:][RACSignal+Operations]

RACSignal *letters = [@"A B C D E F G H I"componentsSeparatedByString:@" "].rac_sequence.signal;// The new signal only contains:123456789//// But when subscribed to, it also outputs: A B C D E F G H IRACSignal *sequenced =[[letters? ? doNext:^(NSString *letter) {? ? ? ? NSLog(@"%@", letter);? ? }]? ? then:^{return[@"1 2 3 4 5 6 7 8 9"componentsSeparatedByString:@" "].rac_sequence.signal;? ? }];

sequenced.signal subscribeNext:^(id x){

NSLog(@“%@“, x); //輸出1 2 3 4 5 6 7 8府阀，并不會輸出A B C D E F G H I

}

執(zhí)行完doNext:中的方法后，返回一個新的signal給原來的信號芽突，并去執(zhí)行subscribeNext中的相應方法

10.[+merge:][RACSignal+Operations]

將兩個信號流合成一個信號流

RACSubject*letters= [RACSubject subject];RACSubject*numbers= [RACSubject subject];RACSignal*merged= [RACSignal merge:@[letters, numbers ]];//Outputs: A1B C2[merged subscribeNext:^(NSString*x) {? ? NSLog(@"%@", x);}];[letters sendNext:@"A"];[numbers sendNext:@"1"];[letters sendNext:@"B"];[letters sendNext:@"C"];[numbers sendNext:@"2"];

[-subscribeNext:]相當于水管出水口试浙，當[-sendNext:]有水注入時，水管出口就會有相應的水流出寞蚌。

11.[+combineLatest:][RACSignal+Operations] and [+combineLatest:reduce:]

觀察所有信號的狀況田巴，當有信號發(fā)生改變時，會將最后改變的信號發(fā)送給監(jiān)聽者挟秤。

RACSubject*letters= [RACSubject subject];RACSubject*numbers= [RACSubject subject];RACSignal*combined= [RACSignal? ? combineLatest:@[letters, numbers ]? ? reduce:^(NSString*letter, NSString*number) {return[letter stringByAppendingString:number];? ? }];//Outputs: B1 B2 C2 C3[combined subscribeNext:^(idx) {? ? NSLog(@"%@", x);}];[letters sendNext:@"A"];[letters sendNext:@"B"];[numbers sendNext:@"1"];[numbers sendNext:@"2"];[letters sendNext:@"C"];[numbers sendNext:@"3"];

12.[-switchToLatest][RACSignal+Operations]

用于信號和信號之間固额，總是選擇最新的信號給另一個。

RACSubject*letters= [RACSubject subject];RACSubject*numbers= [RACSubject subject];RACSubject*signalOfSignals= [RACSubject subject];RACSignal*switched= [signalOfSignals switchToLatest];//Outputs: A B1D [switched subscribeNext:^(NSString*x) { ??? NSLog(@"%@",x);}];[signalOfSignals sendNext:letters];[letters sendNext:@"A"];[letters sendNext:@"B"];[signalOfSignals sendNext:numbers];[letters sendNext:@"C"];[numbers sendNext:@"1"];[signalOfSignals sendNext:letters];[numbers sendNext:@"2"];[letters sendNext:@"D"];