Passing Data from App delegate to View Controller

Question

I need to Pass an string from App delegate to my Initial View Controller , Can somebody listed me the best way to do it , also i tried to Save and Retrieve using NS user Defaults, but i doesn't work out properly .

It's not for some reason. The reason is quite explicit in that the purpose of the app's delegate is to respond to changes in the app's state. Using it as a dumping ground for data and constants is poor form and leads to a dependency on an object that isn't a contributing citizen in the MVC paradigm. — Tyten, Feb 10 '15 at 21:29

score 30 · Accepted Answer · answered Feb 24 '13 at 08:34

30

Interface:

@interface MyAppDelegate : NSObject  {
  NSString *myString;
}
@property (nonatomic, retain) NSString *myString;
...
@end

and in the .m file for the App Delegate you would write:

@implementation MyAppDelegate
@synthesize myString;
    myString = some string;
@end

Then, in viewcontroller.m file you can fetch:

MyAppDelegate *appDelegate = (MyAppDelegate*)[[UIApplication sharedApplication] delegate];
someString = appDelegate.myString;  //..to read
appDelegate.myString = some NSString;     //..to write

answered Feb 24 '13 at 08:34

Skanda

872
13
21

2

This post just saved my day. Thanks a lot friend. – Avijit Jan 07 '14 at 11:47
1

Your answer should contain written in capital letters: "My method is dangerous and bad practice, because it breaks encapsulation and creates global state." – Tomasz Bąk Dec 17 '15 at 16:00

RyanPliske · Answer 2 · 2015-02-10T19:24:46.060

Here it is for Swift:

View Controller

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

Furthermore, if you have an object that you want to pass between view controllers (for example, I had CloudKit data I wanted to share) add this to the App Delegate:

    /* Function for any view controller to grab the instantiated CloudDataObject */
func getCloudData() ->CloudData{
    return cloudDataObject
}

Then back in the View Controller

var model : CloudData = self.appDelegate.getCloudData()

score 14 · Answer 3 · answered Feb 24 '13 at 08:53

14

You can access your root view controller like this from the app delegate:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    MyViewController* mainController = (MyViewController*)  self.window.rootViewController;
    [mainController passData:@"hello"];

    return YES;
}

answered Feb 24 '13 at 08:53

Odrakir

4,254
1
20
52

passData from where? How is declared? – Daniele Tentoni Mar 05 '20 at 11:03

Mu Sa · Answer 4 · 2018-11-28T09:40:14.773

Using Swift 4.2:

Passing Data from AppDelegate to ViewController:

let yourViewController = self.window?.rootViewController as? YourViewController
yourViewController?.passData(YOUR_DATA) // pass data
let data = yourViewController?.getData() // access data

Passing Data from ViewController to AppDelegate:

let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.passData(YOUR_DATA) // pass data
let data = appDelegate.getData() // access data

Add below code to YourViewController or AppDelegate:

private var data : String? // String? or any type you want
func getData() -> String? {
    return data
}
func passData(_ data : String?) {
    self.data = data
}

Passing Data from App delegate to View Controller

4 Answers4

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