objective c - How to merge multiple signal and stop on first next but not to stop on first error? -

i have number of network requests , 1 or more of them return valid data , possible return error. how can combine request stop once first valid returned data not stop in case of error.

i have try this:

[[racsignal merge:@[sigone, sigtwo, sigthree]]         subscribenext:^(ractuple *mydata){             nslog(@"data received");         } error:^(nserror *error) {             nslog(@"e %@", error);         }         completed:^{             nslog(@"they're done!");         }      ]; 

my problems:

• if 1 of signals returns first error no next send. not desired because 1 of other signals return valid data.
• if 3 return valid data subscribenext called 3 times stop got valid data (to reduce network traffic)

try this:

[[[[racsignal merge:@[[sigone catchto:[racsignal empty]],                        [sigtwo catchto:[racsignal empty]],                        [sigthree catchto:[racsignal empty]]]]                            repeat] take:1]     subscribenext:^(ractuple *mydata){         nslog(@"data received");     } error:^(nserror *error) {         nslog(@"e %@", error);     }     completed:^{         nslog(@"they're done!");     }  ]; 

by using catchto:, signals being replaced empty signal when error, causes signal send complete, , doesn't end subscription every other signal. adding repeat, we're getting signal run again if no next events occurred (because of signals errored). adding take:1, signal complete once single next event received.