ios - Returning method object from inside block -

i wondering how following correctly: have method return nsdata object. gets nsdata object uidocument. nsdata object can large, want make sure loaded before response starts. therefore return value of method within block itself. this:

- (nsdata*)getmydata {   myuidocument *doc = [[myuidocument alloc] initwithfileurl:fileurl];   [doc openwithcompletionhandler:^(bool success) {      if (success) {       return doc.myresponsedata; // return method not block     }   }]; } 

this causes error because return apparently refers block's return.

how can accomplish without having make thread blocking wait/while loop?

thanks.

you can't. embrace fact you're trying asynchronous , add completion block parameter getmydata method called when inner completion handler called. (and remove return method signature):

- (void)getmydatawithcompletion:(void(^)(nsdata *data))completion {     myuidocument *doc = [[myuidocument alloc] initwithfileurl:fileurl];     [doc openwithcompletionhandler:^(bool success) {         completion((success ? doc.myresponsedata : nil));     }]; } 

the same problem exists in swift , can add similar completion block:

func getmydata(completion: ((data: nsdata?) -> void) {     data = ...     completion(data) }