Facing an issue with NSURLSessionDataTask with SynchronousRequest in objective-c

Here is my working code with NSURLConnection sendSynchronousRequest :

+ (Inc*)getData:(NSString*)inUUID {
    NSString* urlString = [NSString stringWithFormat:@"/inc/%@", incUUID];
    NSURLRequest* request = [[HttpRequest requestWithRelativePath:urlString] toNSMutableURLRequest];
    NSDictionary* json = [self getJSONForRequest:request];
    return [Inc incFromDictionary:json];
}  
+ (NSDictionary*)getJSONForRequest:(NSURLRequest*)request {
    NSData* responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    return  [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingAllowFragments error:nil];
}  

But, sendSynchronousRequest:request is deprecated.

So that, I used NSURLSessionDataTaskinstead of sendSynchronousRequest. Here, is the code which I implemented:

+ (Inc*)getData1:(NSString*)inUUID {
    NSString* urlString = [NSString stringWithFormat:@"/in/%@", inUUID];
    NSURLRequest* request = [[HttpRequest requestWithRelativePath:urlString] toNSMutableURLRequest];
    //NSDictionary* json = [self getJSONForRequest1:request];
    __block NSDictionary* json;

    dispatch_async(dispatch_get_main_queue(), ^{
        [self getJsonResponse1:request success:^(NSDictionary *responseDict) {
            json = [responseDict valueForKeyPath:@"detail"];;
            //return [Inc incFromDictionary:json];

        } failure:^(NSError *error) {
            // error handling here ...
        }];
    });
    return [Inc incFromDictionary:json];
}  
+ (void)getJsonResponse1:(NSURLRequest *)urlStr success:(void (^)(NSDictionary *responseDict))success failure:(void(^)(NSError* error))failure
{
    NSURLSessionDataTask *dataTask1 = [[NSURLSession sharedSession] dataTaskWithRequest:urlStr completionHandler:^(NSData *data, NSURLResponse *response,
                                                                                                                   NSError *error) {
        NSLog(@"%@",data);
        if (error)
            failure(error);
        else {
            NSDictionary *json  = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
            NSLog(@"%@",json);
            success(json);
        }
    }];
    [dataTask1 resume];    // Executed First
}  

The problem is return statement call in getData1 before finish the api call.

Thanks in advance.

As mentioned in the comments you need a completion handler.

Something like this (untested):

+ (void)getData1:(NSString*)inUUID success:(void (^)(NSDictionary *responseDict))success failure:(void(^)(NSError* error))failure {
    NSString* urlString = [NSString stringWithFormat:@"/in/%@", inUUID];
    NSURLRequest* request = [[HttpRequest requestWithRelativePath:urlString] toNSMutableURLRequest];

    [self getJsonResponse1:request success:^(NSDictionary *responseDict) {
        NSDictionary* json = [responseDict valueForKeyPath:@"detail"];
        success(json);

    } failure:^(NSError *error) {
        failure(error);
    }];
}


+ (void)getJsonResponse1:(NSURLRequest *)urlStr success:(void (^)(NSDictionary *responseDict))success failure:(void(^)(NSError* error))failure
{
    NSURLSessionDataTask *dataTask1 = [[NSURLSession sharedSession] dataTaskWithRequest:urlStr completionHandler:^(NSData *data, NSURLResponse *response,
                                                                                                                   NSError *error) {
        NSLog(@"%@",data);
        if (error)
            failure(error);
        else {
            NSDictionary *json  = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
            NSLog(@"%@",json);
            success(json);
        }
    }];
    [dataTask1 resume];    // Executed First
}

And to call

[MyClass getData1:@"asdf" success:^(NSDictionary *responseDict) {
    dispatch_async(dispatch_get_main_queue(), ^{
        NSDictionary *json = [responseDict valueForKeyPath:@"detail"];
        Inc *inc = [Inc incFromDictionary:json];
        // do something witrh `inc`

    });
} failure:^(NSError *error) {
    // error handling here ...
}];

Consider to use instances and instance methods of your class(es) rather than only class methods.