Performing a Storyboard Segue programmatically

I everybody, I'm currently developing the login and password interface for a new app, and I would like to perform a segue conditionally, only when password and login are ok. I created a Segue in the Storyboard with "push" style, and "loginMainIdentifier". The implementation folder is writen as follows:

    - (IBAction)pushValidateButton:(id)sender {

    if([loginText.text isEqualToString:@""] || [passwordText.text isEqualToString:@""] )
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Identification" message:@"Veuillez completer l'ensemble des cases SVP" delegate:self cancelButtonTitle:@"Revenir" otherButtonTitles:nil];
        alert.alertViewStyle = UIAlertViewStyleDefault;
        [alert show];
    }

    if(![loginText.text isEqualToString:@""] && ![passwordText.text isEqualToString:@""])
    {
    //creation of the request
        NSMutableString *string = [[NSMutableString alloc] initWithCapacity:100];
        NSString *string01 = @"http://89.82.227.112/Vico/login.php?l=&m="; 


        [string appendFormat:string01];
        NSString *string02 = loginText.text;
        NSString *string03 = passwordText.text;

        [string insertString:string03 atIndex:41];
        [string insertString:string02 atIndex:38];

        NSURLRequest *request01=[NSURLRequest requestWithURL:[NSURL URLWithString:string]cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

    //create the connection and start loading data

        NSURLConnection *connection01 = [[NSURLConnection alloc] initWithRequest:request01 delegate:self];
        if(connection01)
        {
        //Create NSMutableData to receive data
        //receiveddata is an instance declared elsewhere
        receivedData = [NSMutableData data];
        }
    }
    [self performSegueWithIdentifier:@"loginMainSegue" sender:self];
}

I dont understand why it doesn't work with [self performSegueWithIdentifier:@"loginMainSegue"