CODEWITHSUNDEEP
iosobjective-cdelegatesprotocols
James
James

Reputation: 301

Setting delegates (for protocols) only works in prepareForSegue?

Most of the information I found involving implementing protocols and delegates involves a step where you do this;

   DestinationViewController *destinationVC = [[destinationViewController alloc] init];
   destinationVC.delegate = self;

But after hours of frustration because I couldn't get it to work I finally stumbled across another way to allocate the destinationVC in prepareForSegue

    DestinationViewController *destinationVC = segue.destinationViewController;
    destinationVC.delegate = self;

Which actually works. What was I doing wrong? It seemed using the first method my delegate was never set to self.

Upvotes: 1

Views: 800

Answers (3)

Imotep
Imotep

Reputation: 2056

When instantiated from a storyboard, the initWithCoder: methid is called, not the init method.

DestinationViewController *destinationVC = [[destinationViewController alloc] init];
   destinationVC.delegate = self;

is how you do when your controller is not from a storyboard: you init it from the code. After that you have to manually handle the transition from your source VC to your destination VC.

DestinationViewController *destinationVC = segue.destinationViewController;
destinationVC.delegate = self;

is how you do when your controller is defined in a storyboard and is the destination of a segue. When you perform a segue, the prepareForSegue: method of the source view controller is called, in which you should configure your destination like you want: setting properties, delegates, passing data,...

Upvotes: 2

Doro
Doro

Reputation: 2413

Here is the basic tutorial about segues, updated for Xcode 6 and above.

https://developer.apple.com/library/ios/recipes/xcode_help-IB_storyboard/chapters/StoryboardSegue.html

When you use storyboards, all necessary context provided by UIStoryboardSegue class. it holds destination view controller for you. So, you must access destination controller throw destinationViewController property.

if you want to manually add controller to your navigation stack:

{
    // binds your viewController from storyboard with local instance
    UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:@"YOUR_STORYBOARD_IDENTIFIER"];
    // set your delegate
    vc.delegate = self;
    // push controller into navigation stack
    [self.navigationController pushViewController:vc animated:YES];

}

Upvotes: 1

Jatin Patel - JP
Jatin Patel - JP

Reputation: 3733

There is two way you can pushController while using UIStoryboard.

Option 1 : taking reference of actually UIViewController from storyboard.

UIViewController *displayTable = [self.storyboard instantiateViewControllerWithIdentifier:@"nextViewcontroller"];
[self.navigationController pushViewController:displayTable animated:YES];

Option 2 : Using Segue

[self performSegueWithIdentifier:@"MySegue" sender:sender];

In your first case you are allocating object and assign delegate. that does't means while performing pushViewController operation same reference is passing. so in that case two different reference is created. so you delegate is point out some other reference that doesn't exist.

may this help you.

Upvotes: 1

Related Questions