ReactiveCocoa操作方法-秩序

doNext:

执行Next之前，会先执行这个Block

doCompleted:

执行sendCompleted之前，会先执行这个Block

[[[[RACSignal createSignal:^RACDisposable*(id subscriber) {

[subscriber sendNext:@"doNext"];

[subscriber sendCompleted];

return nil;

}]

doNext:^(idx) {//执行[subscriber sendNext:@"doNext"];前调用

NSLog(@"beforeDonext");

}]

doCompleted:^{//执行[subscriber sendCompleted];前调用

NSLog(@"afterDonext,beforeComplete");

}]

subscribeNext:^(idx) {

NSLog(@"%@",x);

}];