In swift, how to create a variable in the app delegate in order to retrieve it everywhere in the app?
I am not talking about NSManagedObject
I know that it begin with :
let appDelegate = UIApplication.shared.delegate as! AppDelegate
I have a class Personne
class Personne {
var One: String
var Two: Float
}
and another classe to create a Singleton:
class PersonneController {
var shared = Personne()
and in my app, i have created an instance like this:
var personne = Personne()
so every variable is retrieving by
personne.shared.myvariable
How to put personne in the app delegate, in order to retrieve it from everywhere?
1 . Create the instance of your "Personne" Class in AppDelegate
( var persnee = Personne())
2 . create a function in your AppDelegate to which will return instance of AppDelegate
class func appDelegate() -> AppDelegate
{
return UIApplication.shared.delegate as! AppDelegate
}
3 . You can call like this
AppDelegate.appDelegate(). persnee
Inside the class
class AppDelegate..... {
var name:String?
}
Then
let appDelegate = UIApplication.shared.delegate as! AppDelegate
print(appDelegate.name)
But for this it's better to make a singleton class like
class Service {
static let shared = Service()
var name:String?
}
Then
print(Service.shared.name)
or even make it a global variable
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let aVariable = appDelegate.blabla
In my application, a Connection object is initialized in my AppDelegate.swift, applicationDidBecomeActive().
How do I pass that Connection object to my ViewController subclass?
In AppDelegate create a property
private weak var viewController : ViewController?
In the view controller in viewDidLoad assign self to that property
let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.viewController = self
Now you can access the view controller from AppDelegate
Instances like Connection are usually required throughout the application so the better idea is to create a shared instance of the required object and use anywhere we need.
class Connection{
static let sharedConnection = Connection()
....
}
usage:
let connection = Connection.sharedConnection
I'm trying to execute a method present in AppDelegate from my NSViewController class.
I tried this line to access to the AppDelegate :
let appDelegate = UIApplication.shared.delegate as! AppDelegate;
Without success : Use of unresolved identifier 'UIApplication'.
Tried to import UIKit, doesn't works ... cause it's for IOS ?
PS : It's hard to learn how to develop in swift ... a lot of tutorials are for objective C, and the swifts can also be for IOS ...
NSViewController is clearly macOS.
In macOS you get the application delegate with
let appDelegate = NSApp.delegate as! AppDelegate
NSApp is a shortcut for NSApplication.shared
I would like to write in the text or csv (prefer) file the variable from the view controller.
Indeed I am doing a drawing app and I would like to write in the file the current position of the finger.
class ViewController: UIViewController {var lastPoint = CGPoint.zeroPoint ... }
I would like to have access to lastPoint.x and lastPoint.y from the AppDelegate. how I could do that ? Thank you.
Your question is full of confusion but if that's what you are looking for:
You can access the appDelegate by getting a reference to it like that:
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
after that if you have store a property called lastPoint in your appDelegate you can access its components very simply like that:
let x = appDelegate.lastPoint.x
let y = appDelegate.lastPoint.y
If you need to access your viewController properties from the AppDelegate, then I suggest having a reference to your view controller in your appdelegate:
var myViewController: ViewController!
then when your view controller is created you can store a reference to it in the appdelegate property:
If your create your view controller outside of your appDelegate:
Swift 1-2 syntax
var theViewController = ViewController()
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
appDelegate.myViewController = theViewController
Swift 3-4 syntax
var theViewController = ViewController()
let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.myViewController = theViewController
If you create your view controller inside of your appDelegate:
self.myViewController = ViewController()
After that you can access your data from your viewcontroller from your appdelegate just by accessing its property like that:
let x = self.myViewController.lastPoint.x
let y = self.myViewController.lastPoint.y
Swift 3 Update
var theViewController = ViewController()
let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.myViewController = theViewController
You can create a BaseViewController and write this
class BaseViewController {
lazy var appDelegate : AppDelegate {
return UIApplication.shared.delegate as? AppDelegate
}
}
and inherit other viewcontrollers with BaseViewController and access this by
class ViewController : BaseViewController {
override func viewDidLoad() {
super.viewDidLoad()
print(self.appDelegate?.lastPoint.x)
print(self.appDelegate?.lastPoint.x)
}}
I did manage to access my ViewController from the App delegate by creating an instance of ViewController in AppDelegate.swift, like:
var mainViewController = ViewController()
func applicationWillEnterForeground(_ application: UIApplication) {
mainViewController.myVariable = "Hello".
}
Still, I don't understand how does the AppDelegate "know" that mainViewController is supposed to point to that particular ViewController. As my application has a single view and a single ViewController, that's fine, but what it I had multiple ViewControllers associated with different UIViews? Appreciate if anyone here can shed a light into that.
Best Regards,
Andre
How do I get a reference to AppDelegate in Swift?
Ultimately, I want to use the reference to access the managed object context.
The other solution is correct in that it will get you a reference to the application's delegate, but this will not allow you to access any methods or variables added by your subclass of UIApplication, like your managed object context. To resolve this, simply downcast to "AppDelegate" or what ever your UIApplication subclass happens to be called. In Swift 3, 4 & 5, this is done as follows:
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let aVariable = appDelegate.someVariable
Swift 4.2
In Swift, easy to access in your VC's
extension UIViewController {
var appDelegate: AppDelegate {
return UIApplication.shared.delegate as! AppDelegate
}
}
Convenience Constructors
Add in AppDelegate Class at the end of code
Swift 5.7
func appDelegate() -> AppDelegate {
return UIApplication.shared.delegate as! AppDelegate
}
To use AppDelegate reference anywhere in code?
For example: Call AppDelegate Method named setRoot
appDelegate().setRoot()
This could be used for OS X
let appDelegate = NSApplication.sharedApplication().delegate as AppDelegate
var managedObjectContext = appDelegate.managedObjectContext?
It's pretty much the same as in Objective-C
let del = UIApplication.sharedApplication().delegate
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
Appart from what is told here, in my case I missed import UIKit:
import UIKit
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
}
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.
}
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
Make sure you import UIKit
let appDelegate = UIApplication.sharedApplication().delegate! as! AppDelegate
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"
extension AppDelegate {
// MARK: - App Delegate Ref
class func delegate() -> AppDelegate {
return UIApplication.shared.delegate as! AppDelegate
}
}
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 !!!
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
In Swift 3.0 you can get the appdelegate reference by
let appDelegate = 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
}
}
In the Xcode 6.2, this also works
let appDelegate = UIApplication.sharedApplication().delegate! as AppDelegate
let aVariable = appDelegate.someVariable