how to pass multiple values with a notification in swift

Question

How to send a number and a String through a notification ...

let mynumber=1;
let mytext="mytext";
NSNotificationCenter.defaultCenter().postNotificationName("refresh", object: ?????????????);

and receive the values in the receiver ?

func refreshList(notification: NSNotification){
        let receivednumber=??????????
        let receivedString=?????????
    }

Answer 1

You could wrap them in an NSArray or a NSDictionary or a custom Object.

Eg:

let mynumber=1;
let mytext="mytext";

let myDict = [ "number": mynumber, "text":mytext]

NSNotificationCenter.defaultCenter().postNotificationName("refresh", object:myDict);

func refreshList(notification: NSNotification){
    let dict = notification.object as! NSDictionary
    let receivednumber = dict["number"]
    let receivedString = dict["mytext"]
}

Answer 2

Swift 4 or later

Declare a notification name to be used

extension Notification.Name {
    static let refresh = Notification.Name("refresh")
}

---

Add an observer for that name in your view controller viewDidLoad method and a selector to get the notification object

NotificationCenter.default.addObserver(self, selector: #selector(refreshList), name: .refresh, object: nil)

---

@objc func refreshList(_ notification: Notification) {
    if let object = notification.object as? [String: Any] {
        if let id = object["id"] as? Int {
            print(id)
        }
        if let email = object["email"] as? String {
            print(email)
        }
    }
}

---

Post your notification with your object:

let object: [String: Any] = ["id": 1, "email": "abc@def.com"]
NotificationCenter.default.post(name: .refresh, object: object)

Answer 3

You can use the userInfo property of Notification:

NotificationCenter.default.post(name: Notification.Name("refresh"),
                                object: nil,
                                userInfo: ["number":yourNumber, "string":yourString])

and to retrieve:

func refreshList(notification: Notification){
    let receivednumber = notification.userInfo?["number"] as? Int ?? 0
    let receivedString = notification.userInfo?["string"] as? String ?? ""
}

Answer 4

Actually there are a lot of way to do this. One of them is to pass an array of objects like :

let arrayObject : [AnyObject] = [mynumber,mytext]

NSNotificationCenter.defaultCenter().postNotificationName("refresh", object: arrayObject)

func refreshList(notification: NSNotification){

    let arrayObject =  notification.object as! [AnyObject]

    let receivednumber = arrayObject[0] as! Int
    let receivedString = arrayObject[1] as! String
}

Answer 5

Swift 4.0, I am passing single key:value, you can add multiple keys and values.

   NotificationCenter.default.post(name:NSNotification.Name(rawValue: "updateLocation"), object: ["location":"India"])

Adding Observer and Method definition. You also need to remove observer.

NotificationCenter.default.addObserver(self, selector: #selector(getDataUpdate), name: NSNotification.Name(rawValue: "updateLocation"), object: nil)

@objc func getDataUpdate(notification: Notification) {
        guard let object = notification.object as? [String:Any] else {
            return
        }
        let location = object["location"] as? String
        self.btnCityName.setTitle(location, for: .normal)

        print(notification.description)
        print(notification.object ?? "")
        print(notification.userInfo ?? "")
    }

Answer 6

Swift 4.0

First create a dictionary for multiple values.

let name = "Abhi"
let age = 21
let email = "abhi@xyz.com"
let myDict = [ "name": name, "age":age, "email":email]
// post myDict
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "post"), object: nil, userInfo: myDict)

Add observer in other ViewController

NotificationCenter.default.addObserver(self, selector: #selector(doThisWhenNotify(notification:)), name: NSNotification.Name(rawValue: "post"), object: nil)

func doThisWhenNotify(notification : NSNotification) {
    let info = notification.userInfo
    print("name : ",info["name"])
    print("age : ",info["age"])
    print("email : ",info["email"])

}