NSUrlsession fired, url not called, nevertheless result - ios

Question

I have this method for getting JSON data from a URL:
-(void)getJsonResponse:(NSString *)urlStr success:(void (^)(NSDictionary *responseDict))success failure:(void(^)(NSError* error))failure
{
NSURLSession *session = [NSURLSession sharedSession];
NSURL *url = [NSURL URLWithString:urlStr];
NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:url];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
//NSLog(#"%#",data);
if (error) {
failure(error);
NSLog(#"Error: %#", [error localizedDescription]);
}
else {
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
//NSLog(#"%#",json);
success(json);
}
}];
[dataTask resume];
}
In myViewController, viewWillAppear I call this method as such:
NSString * URLString = #"my.valid.url";
[self getJsonResponse:URLString success:^(NSDictionary *result) {
//here some code when succesful
} failure:^(NSError *error) {
NSLog(#"Something terrible happened");
}];
}
That works fine, but only ONCE:
When I leave myViewController, and enter it again,
viewWillAppear is called, and subsequentially
[self getJsonResponse:... is called
my code in the success block is executed
However: monitoring the network activity with Charles, I notice, that no call is made to my.valid.url.
What gives? Should I invalidated the shared session? If so, when?

Answer 1

set NSURLSessionConfiguration chachePolicy to NSURLRequestReloadIgnoringCacheData and try again. Here is the good resource to understand about Http-caching. Read documentation given in apple guide as well.
NSURLSessionConfiguration *config = NSURLSessionConfiguration.defaultSessionConfiguration;
config.requestCachePolicy = NSURLRequestReloadIgnoringCacheData;
NSURLSession *session = [NSURLSession sessionWithConfiguration:config];