Returning a BOOL method inside a block? - ios

Question

I have this bool method that returns a yes or no for an inputted string.
I'm successfully able to return a YES or a NO, but I cannot seem to able to make a network connection and return a YES or a NO depending on the server's response.
I tried using __block and I don't feel like that will wait for the web request to finish, is there a way to return YES or NO in the success block without it giving me the error:
Incompatible block pointer types sending 'BOOL(^)(NSURLSessionTask*__strong, NSError __strong' to parameter of the type 'void(^)(NSURLSessionTask...)
-(BOOL)customResponseForString:(NSString *)text {
__block BOOL response_available;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
manager.responseSerializer = [AFHTTPResponseSerializer serializer];
[manager.responseSerializer setAcceptableContentTypes:[NSSet setWithObject:#"text/plain"]];
[manager GET:[NSString stringWithFormat:#"http://example.com/response.php?input=%#", text] parameters:nil success:^(NSURLSessionDataTask *task, id responseObject) {
NSDictionary *response = [NSJSONSerialization JSONObjectWithData:responseObject options:NSUTF8StringEncoding error:nil];
response_available = (BOOL)response[#"response_available"];
if (response_available) {
[session sendTextSnippet:response[#"response"] temporary:NO scrollToTop:NO dialogPhase:#"Summary"];
} else {
response_available = NO;
}
[session sendTextSnippet:[[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding] temporary:NO scrollToTop:NO dialogPhase:#"Summary"];
[session sendRequestCompleted];
} failure:^(NSURLSessionDataTask *task, NSError *error) {
//return NO;
}];
});
return response_available;
}

Answer 1

Your block definition syntax is probably erroneous, because you can definitely return a BOOL along other parameters in a block.
- (void)fetchCurrentUserWithCompletion:(void (^)(BOOL success, User *user))completion;
This method would be called like this:
[self.userProfileController fetchCurrentUserWithCompletion:^(BOOL success, User *user) {
if (success) {
NSLog(#"Current User Name: %#", user.fullName);
}
}];
If you use AFNetworking, check the AFHTTPRequestOperation object that handle completionBlocks:
[requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
User *user = [self userFromResponseObject:responseObject];
if (completion) completion(YES, user);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (completion) completion(NO, user);
}];

Answer 2

Because you are implicitly initializing response_available to NO and then using an async GCD call, your method as written will always immediately return NO without waiting for the request to finish. Note: switching to dispatch_sync won't help either because AFNetworking will queue the GET request asynchronously either way.
Best Approach
Add a completion block argument to customResponseForString:. Then simply execute your completion block in the success or failure blocks of the AFHTTPRequestOperation.
Workable Approach (use caution!)
It is possible to make customResponseForString: wait for a response to the network request, but you will have significant issues if it is ever called from the main thread.
First you create a dispatch group and tell it you are starting some long-running work:
dispatch_group_t networkGroup = dispatch_group_create();
dispatch_group_enter(networkGroup);
Then you need to make your network request and when it completes tell the group that the work is finished with dispatch_group_leave():
[manager GET:[NSString stringWithFormat:#"http://example.com/response.php?input=%#", text] parameters:nil success:^(NSURLSessionDataTask *task, id responseObject) {
NSDictionary *response = [NSJSONSerialization JSONObjectWithData:responseObject options:NSUTF8StringEncoding error:nil];
response_available = (BOOL)response[#"response_available"];
if (response_available) {
[session sendTextSnippet:response[#"response"] temporary:NO scrollToTop:NO dialogPhase:#"Summary"];
} else {
response_available = NO;
}
[session sendTextSnippet:[[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding] temporary:NO scrollToTop:NO dialogPhase:#"Summary"];
[session sendRequestCompleted];
dispatch_group_leave(networkGroup);
} failure:^(NSURLSessionDataTask *task, NSError *error) {
response_available = NO;
dispatch_group_leave(networkGroup);
}];
Before your original method returns, tell it to wait for the entire group to finish processing:
dispatch_group_wait(networkGroup, DISPATCH_TIME_FOREVER);
return response_available;
You could adjust this time interval as needed or leave it at DISPATCH_TIME_FOREVER to let the network request time out on its own.