NSURLSession synchronous calls - objective-c

Question

I am not sure seen a clean answer to this. I know how to use blocks, and completion handlers, however for this I cannot use them and need to call the method synchronously :
- (void)codePathWithURL:(NSURLRequest *)request {
// Create session
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
config.URLCache = nil;
config.requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
NSURLSession *urlSession = [NSURLSession sessionWithConfiguration:config delegate:nil delegateQueue:nil];
// Using semaphores
dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
NSURLSessionDataTask *sessionTask = [urlSession dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
responseData = data;
httpResponse = (NSHTTPURLResponse *)response;
outError = error;
dispatch_semaphore_signal(semaphore);
}];
[sessionTask resume];
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
// do something with data
}
The problem I see here it is locks the main thread. How do I make this so that the main thread is not blocked?

Answer 1

Just a quick and dirty attempt to help you get going ... maybe use a condition?
// Call this on the background NOT on the main thread
- ( ... ) some message
{
// Added stuff
__block BOOL done = NO; // ... use now to set data as well
__block NSString * data; // ... or whatever is needed
NSCondition * condition = NSCondition.new;
// Your original stuff
// Create session
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
config.URLCache = nil;
config.requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
NSURLSession *urlSession = [NSURLSession sessionWithConfiguration:config delegate:nil delegateQueue:nil];
NSURLSessionDataTask *sessionTask = [urlSession dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
responseData = data;
httpResponse = (NSHTTPURLResponse *)response;
outError = error;
// Added stuff
condition.lock;
done = YES;
// Set data
data = ... something ...
condition.broadcast;
condition.unlock;
}];
[sessionTask resume];
// New stuff
condition.lock;
while ( ! done )
{
condition.wait;
}
condition.unlock;
// something like ...
return data;
...