How to check if NSURLSessionDataTask is complete? - objective-c

Question

I am getting a n number of json data, and once the whole thing is downloaded or the process of getting the json is complete I need to update the UI of the tableView
for(int i = 1;i <= self.numberOfEpisodes;i++)
{
NSString *endPoint = [[[[urlJson stringByAppendingString:getEpisodes]stringByAppendingString:title]stringByAppendingString:#"&episodeNumber="]stringByAppendingString:[NSString stringWithFormat:#"%i",i]];
endPoint = [endPoint stringByReplacingOccurrencesOfString:#" " withString:#"%20"];
NSLog(#"End point %#",endPoint);
[downloadJson:endPoint WithHandler:^(__weak id result)
{
NSArray *episodeArray =result;
if(episodeArray && episodeArray.count > 0)
{
for(NSDictionary *dictionary in episodeArray)
{
//parse stuff here
}
}
if(i == self.numberOfEpisodes)
{
//update UI
}
}];
}
The problem is in this line if(i == self.numberOfEpisodes). I don't know why the integer i is not arranged from 1 to the self.numberOfEpisodes. Instead it is a random number from 1 to self.numberOfEpisodes. So is there another way how to check if the getting of the json is complete?
(void)getJson:(NSString *)urlString WithHandler:(void(^)(__weak id result))handler
{
NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate: nil delegateQueue: [NSOperationQueue mainQueue]];
NSURL * url = [NSURL URLWithString:urlString];
NSMutableURLRequest * urlRequest = [NSMutableURLRequest requestWithURL:url];
[urlRequest setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[urlRequest setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[urlRequest setHTTPMethod:#"GET"];
NSURLSessionDataTask * dataTask =[defaultSession dataTaskWithRequest:urlRequest
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(error == nil)
{
id returnedObject = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableLeaves error:nil];
handler(returnedObject);
}
else{
NSLog(#"error %#",error);
}
}];
[dataTask resume];
}

Answer 1

Yes there is one way to achieve this by dispatch_group_t
//Creat group
dispatch_group_t group = dispatch_group_create();
for(int i = 1;i <= self.numberOfEpisodes;i++)
{
//Enter group
dispatch_group_enter(group);
NSString *endPoint = [[[[urlJson stringByAppendingString:getEpisodes]stringByAppendingString:title]stringByAppendingString:#"&episodeNumber="]stringByAppendingString:[NSString stringWithFormat:#"%i",i]];
endPoint = [endPoint stringByReplacingOccurrencesOfString:#" " withString:#"%20"];
NSLog(#"End point %#",endPoint);
[downloadJson:endPoint WithHandler:^(__weak id result)
{
NSArray *episodeArray =result;
if(episodeArray && episodeArray.count > 0)
{
for(NSDictionary *dictionary in episodeArray)
{
//parse stuff here
}
}
// Then Leave group
dispatch_group_leave(group);
}];
}
//Here you will be notified after it's done
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
// Do whatever you need to do when all requests are finished
//Update UI
});