CODEWITHSUNDEEP
objective-cswiftstoryboard
AbaEesa
AbaEesa

Reputation: 998

I don't want to reload view controller

I'm using storyboard & segue to go from "HomeVC" to "MapVC".

HomeVC - > segue -> MapVC

And since navigation controller is embedded, MapVC automatically get back button.

Now when I'm again coming from HomeVC->MapVC, MapVC is getting reloaded. Which I don't want. Is there any way to avoid doing it programmatically.

Upvotes: 0

Views: 111

Answers (5)

vaibhav
vaibhav

Reputation: 4096

ViewController always loaded in stack first in last out so when you connect any viewController using push segue firstly it loads the whole viewController inside the memory and when you go back to previously loaded view it will not load again so the process goes so on.

Here is atrick if you opt. You need to do just set the NSUserDefault key true using dispatch_once GCD block inside MapVC viewDidLoad method accordingly and check before it loads.

Example:

// MapVC viewController
- (void)viewDidLoad {
    [super viewDidLoad];
    static dispatch_once_t pred;
         static id shared = nil;
        dispatch_once(&pred, ^{
            // set the key true here
    });    

    if([[[NSUserDefaults standardUserDefaults] valueForKey:@"yourKey"] isEqualToString:@"true"]){
        // code here which you do not wish to execute again and again
        // Note: set the key false here so this block will not execute again
    }

}

Note: set the key true again somewhere else if you want to execute that particular code again.

Upvotes: 0

gnasher729
gnasher729

Reputation: 52622

What do you actually want to achieve? Do you not want to display the view of MapVC?

If you stored some state in the MapVC that you are losing, then you are doing something very, very wrong. VC stands for View Controller. It controls the view. It must never, ever contain your data. So deleting one view controller and creating a new one should be absolutely painless.

Upvotes: 0

donnywals
donnywals

Reputation: 7591

If you're using Storyboard Segues, a new instance of your MapVC will be created every time the Segue is executed. That's just how a Segue works. To solve it you could keep a strong reference to your MapVC in the HomeVC and push that instead. The steps involved are to remove the Segue in your storyboard and assign a Storyboard Identifier on your MapVC. You probably want to create an @IBAction to added to a button to trigger the push. Let's say you set "idMapVC" as the identifier for your MapVC in your storyboard. You'd end up with code like this:

class HomeVC: UIViewController {
    var mapVC: MapVC?

    override func viewDidLoad() {
        super.viewDidLoad()

        mapVC = storyboard?.instantiateViewController(withIdentifier: "idMapVC") as? MapVC
    }

    @IBAction func pushTheMap() {
        guard let mapVC = self.mapVC
            else { return }

        navigationController?.pushViewController(mapVC, animated: true)
    }
}

Upvotes: 0

Daij-Djan
Daij-Djan

Reputation: 50129

I'd not use a segue but an IBAction and do the push manually:

e.g.

  1. hook up a UIButton (or whatever) to trigger @IBAction func buttonClicked(sender: UIButton!)

  2. keep a reference to mapVC as an outlet: @IBOutlet var mapVC:MyMapViewController! [note: you could also initialize the VC manually]

  3. implement the action to push the same mapVC

    @IBAction func buttonClicked(sender: UIButton!) {
    navigationController.pushViewController(mapVC, animated:true)
}

IMHO easiest / pragmatic

alternative idea: keep the segue, but connect it to a blank VC. in prepareForSegue add mapVC as a child of the segue's destinationViewController

IMO this is bad

best way I think: make the mapVC correctly persist and reload it's view based on some state you save in the homeVC.. e.g. keep visibleRegion

IMHO this is best and is how VC's are meant to be used

Upvotes: 2

PGDev
PGDev

Reputation: 24341

When you push MapVC from HomeVC, a new object of MapVC is created each time. Its not that MapVC is reloaded, instead a new instance is created each time.

Upvotes: 1

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