Slow view switch using UIViewController - ios

Question

I'm working on my first app that integrates with a web service. Right now I have two views with their respective view controllers. I have a login view, which is where users will login to the app and I will verify and store there login credentials and I have a main view which shows all the users info from the web service. My two views work correctly individually however after verifying the credentials of the user on my login view I want to switch views to my login view. To do this I'm using UIViewController. Here is my code for when the login button is pressed:
-(IBAction)logIn:(id)sender{
//Show network activity is happening
UIApplication *application = [UIApplication sharedApplication];
application.networkActivityIndicatorVisible = YES;
//Validate credentials
[_loginNetworkingContorller checkCredentialsWithUsername:self.username.text withPassword:self.password.text completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(!error){
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
//if we get back a successful status code save username and password in keychain.
NSLog(#"SUCESS");
NSDictionary *credentials = #{self.username.text: self.password.text};
[KeychainUserPass save:#"INSERT APP NAME HERE" data:credentials];
NSLog(#"go to new page");
//print response from webservice for debugging purposes
NSMutableDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", jsonObject);
//switch to new view controller
UIViewController *mainController = [[RDMainViewController alloc] initWithNibName:#"RDMainViewController" bundle:nil];
[self.navigationController pushViewController:mainController animated:NO];
}
else{
//Error case, handle it.
NSLog(#"ERROR");
}
}
else{
//Error case, handle it.
NSLog(#"ERROR");
}
}];
}
And here checkCredentialsWithUsername method:
-(void)checkCredentialsWithUsername:(NSString *)username withPassword:(NSString *)password completionHandler:(void (^)(NSData *data,NSURLResponse *response, NSError *error))myCompletion
{
//Create request URL
NSString *requestString = #"WEB_SERVICE_URL";
NSURL *url = [NSURL URLWithString:requestString];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
//Store password and user name for authentication
NSData *userPasswordData = [[NSString stringWithFormat:#"%#:%#", username, password] dataUsingEncoding:NSUTF8StringEncoding];
NSString *base64EncodedCredential = [userPasswordData base64EncodedStringWithOptions:0];
NSString *authString = [NSString stringWithFormat:#"Basic %#", base64EncodedCredential];
//Create an NSURL session
NSURLSessionConfiguration *sessionConfig=[NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.HTTPAdditionalHeaders=#{#"Authorization":authString};
self.session=[NSURLSession sessionWithConfiguration:sessionConfig];
NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
myCompletion(data, response, error);
}];
[dataTask resume];
}
My issue is that it's taking an incredibly long time to switch views. Like sometimes over a minute. At first I thought it was the network connection but then I printed the data I was receiving from the web service and it was appearing very quickly. Even after I printed the data it was still taking a very long time for views to switch. I'm not really sure why but I think it has to do with the way I'm doing my blocks. Any idea why it's taking me such a long time to switch views?
Any help would be greatly appreciated.

Answer 1

#Danyun was right. I needed to do the following:
if (httpResp.statusCode == 200) {
//if we get back a successful status code save username and password in keychain.
NSLog(#"SUCESS");
NSDictionary *credentials = #{self.username.text: self.password.text};
[KeychainUserPass save:#"INSERT APP NAME HERE" data:credentials];
NSLog(#"go to new page");
//print response from webservice for debugging purposes
NSMutableDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", jsonObject);
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
//test to make sure we are on the main Queue for UI update
//switch to the new view controller
UIViewController *mainController = [[RDMainViewController alloc] initWithNibName:#"RDMainViewController" bundle:nil];
[self.navigationController pushViewController:mainController animated:NO];
}];
}