ios - How to send error in signal chain -

i have signal contains integer values. value of -1 indicates invalid result, i'd to, instead of passing -1 along value, send error. way subscribes b receive valid integers through subscribenext: , errors through subscribeerror:.

i think know how racsubject:

racsequence *a = [@[ @(2), @(6), @(5), @(-1), @(4) ] rac_sequence]; racsubject *b = [racsubject subject]; [a subscribenext:^(nsnumber *val) {     if ( [val integervalue] == -1 ) {         [b senderror:[nserror errorwithdomain:@"mydomain" code:0 userinfo:nil]];     } else {         [b sendnext:val];     } } error:^(nserror *error) {     [b senderror:error]; } completed:^{     [b sendcompleted]; }]; 

i'm wondering if there's more "inline" way along lines of:

racsequence *a = [@[ @(2), @(6), @(5), @(-1), @(4) ] rac_sequence]; racsignal *b = [a filter:^bool(id val) {     if ( [val integervalue] == -1 ) {         //fixme: send error b's subscriber(s)         return no;     } else {         return yes;     } } 

the primary method using -flattenmap:, similar how you've written -filter: above. using example:

racsignal *b = [a flattenmap:^(nsnumber *number) {     if (number.intvalue == -1) {         return [racsignal error:[nserror errorwithdomain:@"mydomain" code:0 userinfo:nil]];     } else {         return [racsignal return:number];     } }]; 

update

alternatively, using newer -try: operator:

racsignal *b = [a try:^(nsnumber *number, nserror **error) {     if (number.intvalue == -1) {         *error = [nserror errorwithdomain:@"mydomain" code:0 userinfo:nil];         return no;     }      return yes; }];