Make periodic server requests with NSURLSessionDataTask and dispatch_source timer - ios

Question

Need some help and explanation, because i'm really stuck in my question. i need to make this:
1) I make one request to the server, get some response and then i want to make another request every 7 seconds(example). also get some response. if it satisfy several conditions -> stop timer and do some stuff.
Main problem is that timer never stops, despite the fact that all in all i get response right. i assume that i use GCD incorrectly. because in debug this code behaves really strange.
What i have done:
This is my request function(it became like this after i read about 50 links how to do similar things)
-(void)makeRequestWithURL:(NSString*)urlString andParams:(NSString*)params andCompletionHandler:(void(^)(NSDictionary *responseData, NSError *error))completionHnadler{
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration];
NSURL *url = [NSURL URLWithString:urlString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
request.HTTPMethod = #"POST";
request.HTTPBody = [params dataUsingEncoding:NSUTF8StringEncoding];
NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if (completionHnadler) {
if (error) {
dispatch_async(dispatch_get_main_queue(), ^{
completionHnadler(nil, error);
});
} else {
NSError *parseError;
json = [NSJSONSerialization JSONObjectWithData:data
options:NSJSONReadingMutableContainers
error:&parseError];
dispatch_async(dispatch_get_main_queue(), ^{
completionHnadler(json, parseError);
});
}
}
}];
[postDataTask resume]; }
I create my timer like this:
dispatch_source_t CreateDispatchTimer(uint64_t interval,
uint64_t leeway,
dispatch_queue_t queue ,
dispatch_block_t block) {
dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
if (timer) {
// Use dispatch_time instead of dispatch_walltime if the interval is small
dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), interval, leeway);
dispatch_source_set_event_handler(timer, block);
dispatch_resume(timer);
}
return timer; }
and called it like this:
-(void)checkForPassenger {
timerSource = CreateDispatchTimer(7ull * NSEC_PER_SEC, 1ull * NSEC_PER_SEC, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
if([self getNotificationsRequest] == YES) {
dispatch_source_cancel(timerSource);
} else {
NSLog(#"go on timer");
}
NSLog(#"Driver checked for passenger!");
}); }
this is the code of periodic response:
-(BOOL)getNotificationsRequest {
NSString *urlString = #"http://primetime.by/temproad/do";
NSString *params = [NSString stringWithFormat:#"event={\"type\": \"in.getNotifications\"}&session_id=%#",session_id];
[self makeRequestWithURL:urlString andParams:params andCompletionHandler:^(NSDictionary *responseData, NSError *error) {
if ([[responseData objectForKey:#"rc"] intValue] == 0) {
NSArray *temp_notifications = [responseData objectForKey:#"notifications"];
if (temp_notifications.count != 0) {
notification = [[Notification alloc] initWithNotification:[[responseData objectForKey:#"notifications"] objectAtIndex:0]];
}
}
}];
if (notification) {
return YES;
} else {
return NO;
} }
and this is what i do in main request:
[self makeRequestWithURL:urlString andParams:params andCompletionHandler:^(NSDictionary *responseData, NSError *error) {
if ([[responseData objectForKey:#"rc"] intValue] == 0) {
route = [[Route alloc] initWithData:responseData];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self checkForPassenger];
});
}
}];
NSLog(#"bye");
maybe explanation is bad so i can answer any question.
thx