How to navigate to a ViewController from NSObject Class in iOS

NSObject file:

.h

@interface NotificationTap : NSObject

-(void)SingleViewController:(UINavigationController *)nav msg:(NSDictionary*)note;

.m

-(void)SingleViewController:(UINavigationController *)nav msg:(NSDictionary*)note

{

    ChatViewController *viewController = [[ChatViewController alloc] init];

    [nav pushViewController:viewController animated:YES];

}

ViewController File:

.h

#import "NotificationTap.h"

@property(nonatomic,retain) NotificationTap *callView;

-(void)callSingleChat:(NSNotification *)note{

    self.callView = [[NotificationTap alloc] init];

    [self.callView SingleViewController:self.navigationController msg:note.object];

}