How to get data to return from NSURLSessionDataTask

Question

I have a registration view controller which handles all the user input and calls a function in another class (wsClass) passing to it, that data as an NSDictionary.

T

Answer 1

This might work.

1. Add an interface variable nsDictVariable for NSDict or whatever you are retrieving in the class
2. Within SendData assign it: self.nsDictVariable = ....

Answer 2

The post completes asynchronously, so your wsClass needs to tell the caller about completion after post is finished. A nice way to do this is to augment the sendData method with a block of code supplied by the caller that should be run upon completion:

Change sendData: to look like this:

// it doesn't return anything, because all it does is launch the post
// but when the post is done, it invokes completion

- (void)sendData:(NSDictionary *)sendDict completion:(void (^)(NSDictionary *))completion {

    // the stuff you're already doing

        NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request
            completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
            // the stuff you're already doing
            // now tell the caller that you're done
            completion(jsonArray);
        }];
    }

The caller now looks like this:

// change the UI to say "I'm busy doing the post"
[ws sendData:testDict completion:^(NSDictionary *responseDict) {
    NSLog(@"this runs later, after the post completes %@", responseDict);
    // change the UI to say "The post is done"
}];

Just a couple of notes about this: (1) I didn't add an error param to the block, you probably should. Check that and invoke the block with either nil and an error, or with the json output and error=nil. (2) Your code assumes that the json result parses as a dictionary. Make sure that's always true before you assume it in code. (3) Class names usually begin with caps.

Answer 3

Try this . This will work well.

-(void)loadDetails
{

NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
[[session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {


    _allVehicleLocationsArray = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];

    [self afterCompleteDoThis];


}] resume];


}

-(void)afterCompleteDoThis{

for (NSDictionary *vehicleDict in _allVehicleLocationsArray) {

    NSLog(@" PPP %@" , [vehicleDict valueForKey:@"vehicleType"]);

}
}

Answer 4

You can use Semaphores for wiating till the block completes the execution and then return the value from function

- (NSDictionary *)sendData:(NSDictionary *)sendDict {
NSMutableString *sendStr = [[NSMutableString alloc] init];

[sendDict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
[sendStr appendFormat:@"&%@=%@", key, obj];
}];

NSLog(@"sendStr is: %@",sendStr);
NSString *noteDataString = [NSString stringWithFormat:@"%@%@",REQUIRED,sendStr];

NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlTest]];
request.HTTPBody = [noteDataString dataUsingEncoding:NSUTF8StringEncoding];
request.HTTPMethod = @"POST";


 let semaphore = dispatch_semaphore_create(0)

NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
// The server answers with an error because it doesn't receive the params
// handle response
if(error == nil)
{
[getReqAlert dismissWithClickedButtonIndex:0 animated:YES];

NSError *e = nil;
jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableLeaves error: &e];

if (!jsonArray) {
NSLog(@"Error parsing JSON: %@", e);
} else {

NSLog(@"resp: %@ = %@",[jsonArray objectForKey:@"status"],[jsonArray objectForKey:@"msg"]);
NSLog(@"Dictionary count: %lu", jsonArray.count);

     dispatch_semaphore_signal(semaphore)
}
}
}];

[postDataTask resume];
 dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
return jsonArray;

}