How to push to one view controller object from multiple view controllers - ios

Question

So I have a view controller FavoritesViewController and I have an instance of that view controller:
FavoritesViewController *FVC=[[FavoritesViewController alloc]init];
If I have two other view controllers, HomeViewController and SettingsViewController how do I have it so that I can push to that one particular instance "FVC" from both view controllers. I guess the real question is how/where can I initialize that instance "FVC" so that it is recognized by both view controllers and don't initialize it in HomeViewController or SettingsViewController.
Thanks

Answer 1

When you look at the MVC pattern, the object that you should really care about sharing is the model, not the controller. Your questions suggests to me that maybe the ViewController is also performing the responsibility of being the model.
If this is true, you might want to create another class (called Favorites, perhaps) and follow the suggestions in some of the previous answers to make it a singleton, if necessary. Doing it this way, rather than making the VC a singleton also has the benefit of working the same way whether you are using storyboards, xib, or code.
Maybe you have a good reason to need to share the VC itself, but I thought it would be worthwhile to question that premise.

Answer 2

If you want a single instance of your favorites view controller that is shared throughout your app, make it a singleton. Do a Google search on the singleton design pattern in iOS. The idea is that you would add a class method sharedFavoritesController that would always return the same instance, and use that.
The class method would look something like this:
+(FavoritesViewController *) sharedFavoritesVC;
{
static FavoritesViewController *_sharedFavoritesVC;
if (! _sharedFavoritesVC)
_sharedFavoritesVC = [[FavoritesViewController alloc] init;
return _sharedFavoritesVC;
}
Then #import the header for your FavoritesViewController class, and any time you need to invoke it, use:
[FavoritesViewController sharedFavoritesVC] to get a pointer to it.

Answer 3

Way 1 :
Declare
extern FavoritesViewController *FVC;
Way 2 :
If this is your rootViewController then in other viewcontrollers
FavoritesViewController *fvc=(FavoritesViewController*)appDelegateObj.rootViewController;
Way 3 :
use singleton
+(FavoritesViewController *) sharedInstance;
{
static FavoritesViewController *SVC;
if (! SVC)
SVC = [[FavoritesViewController alloc] init;
return SVC;
}

Answer 4

You could wrap a singleton pattern around that view controller.
Or, less elegant but more common, instantiate it in you AppDelegate and fetch it from there.
Be aware that the same instance of a view controller can only be once in the stack of view controllers. Plus - in principle - there is nothing wrong with having multiple instances of the same view controller class.
Edit in reply to your comment:
Not that I recommend that but this is how you would fetch a property sharedFavoritesViewController (which may refer to an instance of your FavoritesViewController) when your app delegate class is named MyAppDelegate:
FavoritesViewController localVar = [(MyAppDelegate)[[UIApplication sharedApplication] delegate] sharedFavoritesViewController];