CODEWITHSUNDEEP
iosswift
Brian Hawk
Brian Hawk

Reputation: 806

How can I access an IBOutlet in ViewController from another class?

I have a class that is a GCDAsyncUdpSocketDelegate. Now I'm getting some data thru UDP (in a background thread) and need to display that data with an IBOutlet in my ViewController. But ViewController is just a class. Where is its object instance defined? What is its name? What do I do to access it, or one of its properties, methods? I've seen this UIApplication.sharedApplication().keyWindow?.rootViewController method but this doesn't guarantee the exact ViewController I want to access, I guess.

Upvotes: 0

Views: 358

Answers (2)

Nicolas Miari
Nicolas Miari

Reputation: 16246

I don't know the exact structure of your app, but you could try something like this:

let rootViewController = UIApplication.sharedApplication().keyWindow?.rootViewController

if let customViewController = rootViewController as? CustomViewController {

    customViewController.label.text = theData
}
else{ 
    let customViewController = storyoboard!.instantiateViewControllerWithIdentifier("CustomViewControllerID")
    // (This assumes CustomViewController is defined in the same 
    // storyboard as the view controller running this code. Otherwise, 
    // you need to get a reference to the storyboard first).

    rootViewController.presentViewController(customViewController, animated:true)

    customViewController.label.text = theData
}

EDIT: If the object that receives your asynchronous server data is dettached from your navigation (good call, by the way), you can have it:

  1. Store the data somewhere it will persist even if said object is deallocated (or make said object a singleton, if applicable).

  2. Post a system notification (using NSNotificationCenter) once the data is available, and have your main ViewController "listen to it" (-addObserver:selector:name:object). When the notification is posted and the notification handler is called, your view controller can retrieve the data from its (persistent) location (file, or property of the singleton mentioned above if you chose that route).

  3. Finally, for the case when the data is already available by the time your ViewController is instantiated, check for data availability and retrieve it if present in e.g. your main view controller's viewDidLoad().

Upvotes: 1

Satheesh
Satheesh

Reputation: 11276

There are many ways you can achieve this,

1. Use Protocols or Delegates

You said "I have a class that is a GCDAsyncUdpSocketDelegate." Write a protocol implementation in that class and make your view controller subscribe to that delegate, when you get delegate call back for your GCDAsyncUdpSocketDelegate do neccessary check and fire your custom delegate to the view controller, pass the data as an argument to the delegate method. In the view controller get the data and update the IBOutlet.

2. Use NSNotificationCenter (dirty way of doing things, gotta be careful though)

In your view controller class add an observer for the notification you are going to post like,

NSNotificationCenter.defaultCenter().addObserver(self, selector: "updateUI:", name: "didRecieveDataFromUDP", object: nil)

Add a method in your VC

 func updateUI(notifObject:NSNotification){
  let responseString = notifObject.object
  self.yourOutlet.string = responseString
}

and also remove the notification observer when you are done with the VC. In the GCDAsyncUdpSocketDelegate delegate class when you get the call back with results fire this notification,

  NSNotificationCenter.defaultCenter().postNotificationName("didRecieveDataFromUDP"", object: theResposenObjectYouNeedToSend)

3. Use sharedInstances or mis-use the AppDelegate (not recommended)

Create shared instances or singleton classes that will live through the app lifecycle and use them to store/retrieve data from any class or any thread.

Hope this helps, I wish you choose the first or second way.

Upvotes: 1

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