ReactiveCocoa 谈一下concat

 1  //1.从CoreData中获取数据 2     RACSignal *local = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) { 3         //1.1 获取完成后通知下一步 4         [subscriber sendNext:nil]; 5         [subscriber sendCompleted]; 6         return nil; 7     }]; 8      9     //2.转换数据,这个过程没有理由在mainThread中进行的10     RACSignal *viewModel = [[local subscribeOn:[RACScheduler scheduler]] map:^id(id value) {11         //1.2 将CoreDataModel转换成视图模型12         return nil;13     }];14     15     //3.显示到界面中16     [viewModel subscribeNext:^(id x) {17        18         19     }];20     21     //4.创建一个网络请求22     RACSignal *request = [viewModel then:^RACSignal *{23         return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {24             25             NSURLSessionTask *task = nil;//这里新建一个网络请求26             27             return [RACDisposable disposableWithBlock:^{28                 if (task.state != NSURLSessionTaskStateCompleted) {29                     [task cancel];30                 }31             }];32             33         }];34 35     }];36     37     38 39     //5.避免重复请求,使用MutileConnection转换Signal40     RACMulticastConnection *requestMutilConnection  = [request multicast:[RACReplaySubject subject]];41     [requestMutilConnection connect];42     43     //6.处理服务器结果44     RACSignal *response = [request flattenMap:^RACStream *(id value) {45        //比如response中包含一个state 的枚举字段,判断这货是返回是否有效请求46         47 //        return [RACSignal return:value];48         return [RACSignal error:value];49     }];50     51     //7.更新界面52     [response subscribeNext:^(id x) {53        //再次更新界面54     }];55     56     //8.处理错误57     [response subscribeError:^(NSError *error) {58        //处理错误59     }];

 1     RACSignal *fristSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) { 2         3         NSLog(@"oneSignal createSignal"); 4         [subscriber sendNext:@""]; 5         [subscriber sendCompleted]; 6          7         return [RACDisposable disposableWithBlock:^{ 8             NSLog(@"oneSignal dispose"); 9         }];10     }];11     12     RACMulticastConnection *connection = [fristSignal multicast:[RACReplaySubject subject]];13 14     [connection connect];15     16     [connection.signal subscribeNext:^(id x) {17         NSLog(@"2");18     }];19     20     21     RACSignal *afterConcat = [connection.signal concat:[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {22         [subscriber sendNext:@""];23         return nil;24     }]];25     26     [afterConcat subscribeNext:^(id x) {27         NSLog(@"afterConcat subscribeNext");28     }];

 1     RACSignal *fristSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) { 2         3         NSLog(@"oneSignal createSignal"); 4         [subscriber sendNext:@""]; 5         [subscriber sendCompleted]; 6          7         return [RACDisposable disposableWithBlock:^{ 8             NSLog(@"oneSignal dispose"); 9         }];10     }];11     12     RACMulticastConnection *connection = [fristSignal multicast:[RACReplaySubject subject]];13 14     [connection connect];15     16     [connection.signal subscribeNext:^(id x) {17         NSLog(@"2");18     }];19     20     21     RACSignal *then = [connection.signal then:^RACSignal *{22         23         return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {24             [subscriber sendNext:@""];25             return nil;26         }];27         28     }];29     30     [then subscribeNext:^(id x) {31         NSLog(@"then subscribNext");32     }];