Is there a good way to call an external method after a set time limit for completing the long process outlined below? I would like the long process to stop trying after a set interval and call a method to try something else and wrap up the request.
dispatch_async(dispatch_get_global_queue(0, 0), ^{
//// LONG PROCESS
dispatch_async(dispatch_get_main_queue(), ^{
//// RESULTS PROCESS
});
});
In order to "kill" the process that's running your block, you'll have to check a condition. This will allow you to do cleanup. Consider the following modifications:
dispatch_async(dispatch_get_global_queue(0, 0), ^{
BOOL finished = NO;
__block BOOL cancelled = NO;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 5.0 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
if (!finished) {
cancelled = YES;
}
});
void (^cleanup)() = ^{
// CLEANUP
};
//// LONG PROCESS PORTION #1
if (cancelled) {
cleanup();
return;
}
//// LONG PROCESS PORTION #2
if (cancelled) {
cleanup();
return;
}
// etc.
finished = YES;
dispatch_async(dispatch_get_main_queue(), ^{
//// RESULTS PROCESS
});
});
dispatch_after before it fires and checks the condition?
dispatch_after fires after you've finished processing, it sees that finished is YES, so it just exits and does nothing.dispatch_after items. I'm not sure this particular one would eat many resources; I didn't profile it, so I'm not 100% sure, but it's not doing much. Presumably if you're expecting the processing in the rest of this process to be long enough on average to necessitate a timeout dispatch_after, you won't be calling it many times in a loop.In the ////Long Process change a boolean value (like BOOL finished) to true when finished.
After the call to dispatch_async(...) you typed here, add this:
int64_t delay = 20.0; // In seconds
dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, delay * NSEC_PER_SEC);
dispatch_after(time, dispatch_get_main_queue(), ^(void){
if (!finished) {
//// Stop process and timeout
}
});
In this way, after 20 seconds (or any time you want) you can check if the process is still loading and take some provisions.
if(!finished) after 20 seconds. This could cause problems in a loop situation.dispach_after will fire off that void function to check the boolean "finished" , would there be a way to double back and terminate the request to fire off that function before it happens? To clean up?
I've used this method for Swift:
let delay = 0.33 * Double(NSEC_PER_SEC)
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
dispatch_after(time, dispatch_get_main_queue()) {
//// RESULTS PROCESS
}
