Objective-C present modally segues programmatically - ios

Question

I created a present modally segues in my storyboard like in the image below.
My First scene has a button with an action:
- (IBAction)loginButtonPressed:(id)sender {
[self Login];
}
which goes into this method:
- (void)Login
{
NSString *rawString = [self.idTextField text];
NSCharacterSet *whitespace = [NSCharacterSet whitespaceAndNewlineCharacterSet];
[self.idTextField setText:[rawString stringByTrimmingCharactersInSet:whitespace]];
[userName UserLogin:self.idTextField.text andPassWordExists:self.passwordTextField.text completionHandler:^(id responseObject, NSError *error) {
if (responseObject != nil) {
NSString *userN,*name;
NSArray *object = [responseObject objectAtIndex:0];
userN = [object valueForKey:#"userName"];
name = [object valueForKey:#"name"];
self.idTextField = nil;
self.passwordTextField = nil;
LHAppDelegate *appDelegate = (LHAppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate.loginSession setString:[userN lowercaseString]];
[appDelegate.nameOfUser setString:name];
}else{
[self CustomAlert:#"Sorry Login Failed, User and/or Passsword Incorrect"];
}
[indicatorView stopAnimating];
[indicatorView removeFromSuperview];
indicatorView = nil;
[loadingView removeFromSuperview];
loadingView = nil;
}];
}
What I am trying to do is program so when the user logins in they are present modally to the Tab Bar Controller.
Currently, when I click on the button with the wrong creds, I see my custom alert, but it still brings me to the Tab bar Controller.
Basically what I wanna do is put a condition around the present modally segues. Is this possible?
I found this piece of code:
[self performSegueWithIdentifier: #"MySegue" sender: self];
and I added it to my Login method:
- (void)Login
{
NSString *rawString = [self.idTextField text];
NSCharacterSet *whitespace = [NSCharacterSet whitespaceAndNewlineCharacterSet];
[self.idTextField setText:[rawString stringByTrimmingCharactersInSet:whitespace]];
[userName UserLogin:self.idTextField.text andPassWordExists:self.passwordTextField.text completionHandler:^(id responseObject, NSError *error) {
if (responseObject != nil) {
NSString *userN,*name;
NSArray *object = [responseObject objectAtIndex:0];
userN = [object valueForKey:#"userName"];
name = [object valueForKey:#"name"];
self.idTextField = nil;
self.passwordTextField = nil;
LHAppDelegate *appDelegate = (LHAppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate.loginSession setString:[userN lowercaseString]];
[appDelegate.nameOfUser setString:name];
[self performSegueWithIdentifier: #"MySegue" sender: self];
}else{
[self CustomAlert:#"Sorry Login Failed, User and/or Passsword Incorrect"];
}
[indicatorView stopAnimating];
[indicatorView removeFromSuperview];
indicatorView = nil;
[loadingView removeFromSuperview];
loadingView = nil;
}];
}
still when I login with the wrong creds and it still brings me to the Tab Bar Controller

Answer 1

In the above scenario it will always perform segue unaffected by server response because the segue is performed by button click.
To avoid this do it in the following way:
Delete the segue from button to the UITabBarController and make it
from view controller to the UITabBarController(drag from view
controller to other view conroller).
Now when your getting success in response make the following call
[self performSegueWithIdentifier:#"segueIdentifier" sender:self]
And if you want to pass parameters the perform the following function:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender

Answer 2

One easy way of doing it would be to implement - (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender from the NSSeguePerforming protocol.
If user was not logged in return NO, else return YES, and segue will be performed/user will be taken to the tab bar controller.
EDIT
Since you already have implemented logic for authorising user in login method, I suggest doing what #manish_kumar have suggested.