[swift] How do I get a reference to the app delegate in Swift?

How do I get a reference to the app delegate in Swift?

Ultimately, I want to use the reference to access the managed object context.

In my case, I was missing import UIKit on top of my NSManagedObject subclass. After importing it, I could remove that error as UIApplication is the part of UIKit

Hope it helps others !!!

Try simply this:

Swift 4

// Call the method
(UIApplication.shared.delegate as? AppDelegate)?.whateverWillOccur()

where in your AppDelegate:

// MARK: - Whatever
func whateverWillOccur() {

    // Your code here.

}

In Swift 3.0 you can get the appdelegate reference by

let appDelegate = UIApplication.shared.delegate as! AppDelegate

Swift 4.2

In Swift, easy to access in your VC's

extension UIViewController {
    var appDelegate: AppDelegate {
    return UIApplication.shared.delegate as! AppDelegate
   }
}

This could be used for OS X

let appDelegate = NSApplication.sharedApplication().delegate as AppDelegate
var managedObjectContext = appDelegate.managedObjectContext?

it is very simple

App delegate instance

let app = UIApplication.shared.delegate as! AppDelegate

you can call a method with one line syntax

app.callingMethod()

you can access a variable with this code

app.yourVariable = "Assigning a value"

I use this in Swift 2.3.

1.in AppDelegate class

static let sharedInstance: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

2.Call AppDelegate with

let appDelegate = AppDelegate.sharedInstance

1. Make sure you import UIKit

2. let appDelegate = UIApplication.sharedApplication().delegate! as! AppDelegate

Appart from what is told here, in my case I missed import UIKit:

import UIKit

Here is the Swift 5 version:

let delegate = UIApplication.shared.delegate as? AppDelegate

And to access the managed object context:

    if let delegate = UIApplication.shared.delegate as? AppDelegate {

        let moc = delegate.managedObjectContext
        
        // your code here
        
    }

or, using guard:

    guard let delegate = UIApplication.shared.delegate as? AppDelegate  else {
        return
    }

    let moc = delegate.managedObjectContext
        
    // your code here
    

In the Xcode 6.2, this also works

let appDelegate = UIApplication.sharedApplication().delegate! as AppDelegate

let aVariable = appDelegate.someVariable

Here's an extension for UIApplicationDelegate that avoids hardcoding the AppDelegate class name:

extension UIApplicationDelegate {

    static var shared: Self {    
        return UIApplication.shared.delegate! as! Self
    }
}

// use like this:
let appDelegate = MyAppDelegate.shared // will be of type MyAppDelegate

It's pretty much the same as in Objective-C

let del = UIApplication.sharedApplication().delegate

extension AppDelegate {

    // MARK: - App Delegate Ref
    class func delegate() -> AppDelegate {
        return UIApplication.shared.delegate as! AppDelegate
    }
}

As of iOS 12.2 and Swift 5.0, AppDelegate is not a recognized symbol. UIApplicationDelegate is. Any answers referring to AppDelegate are therefore no longer correct. The following answer is correct and avoids force-unwrapping, which some developers consider a code smell:

import UIKit

extension UIViewController {
  var appDelegate: UIApplicationDelegate {
    guard let appDelegate = UIApplication.shared.delegate else {
      fatalError("Could not determine appDelegate.")
    }
    return appDelegate
  }
}

SWIFT < 3

Create a method in AppDelegate Class for ex

func sharedInstance() -> AppDelegate{
        return UIApplication.sharedApplication().delegate as! AppDelegate
    }

and call it some where else for ex

let appDelegate : AppDelegate = AppDelegate().sharedInstance()

SWIFT >= 3.0

func sharedInstance() -> AppDelegate{
    return UIApplication.shared.delegate as! AppDelegate
}

Convenience Constructors

Add in AppDelegate Class at the end of code

Swift 5

func appDelegate() -> AppDelegate {
    return UIApplication.shared.delegate as! AppDelegate
}

To use AppDelegate reference in your class?

Call AppDelegate Method

appDelegate().setRoot()