Objective-C Implement a timeout in non-blocking way - objective-c

Question

I am invoking an external async function that should invoke a callback once it completes.
However since the function is external, I do not control its implementation and I want to set a timeout for 5 seconds as an example and consider the operation of being timed out if the callback passed to that external async function wasn't invoked during those 5 seconds.
And the only way I currently found is to make the current thread sleep that actually blocks the thread.
Here is an example:
+(void)myFuncWithCompletion:(void (^ _Nonnull)(BOOL))completion{
BOOL timedOut = NO;
BOOL __block finishedAsyncCall = NO;
[someObj someAsyncMethod {
// completion callback
finishedAsyncCall = YES;
if (!timedOut) {
completion(YES);
}
}];
// This is the logic I want to fix. My goal is to make something similar but non-blocking.
long timeoutInSeconds = 5;
long startTime = [[NSDate date] timeIntervalSince1970];
long currTime = [[NSDate date] timeIntervalSince1970];
while (!finishedAsyncCall && startTime + timeoutInSeconds > currTime) {
[NSThread sleepForTimeInterval:0];
currTime = [[NSDate date] timeIntervalSince1970];
}
if (!finishedAsyncCall) {
timedOut = YES;
completion(NO);
}
}

Answer 1

You can use dispatch_after instead of -[NSThread sleepForTimeInterval:]
double delayInSeconds = 5.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC)); // 1
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){ // 2
if (!finishedAsyncCall ) {
timedOut = YES;
completion(NO);
}
});