CODEWITHSUNDEEP
iosswiftperformselector
yang
yang

Reputation: 31

How to use performSelectorInBackground in swift?

import UIKit


class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @objc class myClass:NSObject {

        func myFunc(){
            for var i = 0; i < 10000; i++ {
                print(i,[NSThread.currentThread()]);
            }
        }
    }
    var myObj = myClass()

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        _ = NSThread.init(target: myObj, selector:Selector(myObj.myFunc()), 

    object: nil)
        }
    }

when I run the code above, Xcode has a exception.the information is

[NSThread initWithTarget:selector:object:]: target does not implement selector

how to use performSelectorInBackground in swift ??

Upvotes: 3

Views: 2910

Answers (6)

JonJ
JonJ

Reputation: 1061

Note the latest syntax for performing a task in the background is:

let backgroundQueue = DispatchQueue.global(qos: .background)
backgroundQueue.async {
    // Do stuff in the background
    DispatchQueue.main.async {
        // Pass to the main queue for UI work etc
    }
}

If you're referring to self in the background queue you probably want to add [weak self] in after the .async {.

Upvotes: 0

Guri S
Guri S

Reputation: 1103

This Worked for me 

performSelector(inBackground: #selector(Selection_Button(url:)), with: finalPath2)

Upvotes: 0

gnasher729
gnasher729

Reputation: 52538

Simple answer: You don't. Use dispatch_async.

Upvotes: 2

yang
yang

Reputation: 31

Two points need to pay attention： first, the class which use performSelectorInBackground must inhert NSObject. second,performSelectorInBackground(Selector("myFunc"), withObject: nil) is correct. myFunc is function name.

Upvotes: 0

technerd
technerd

Reputation: 14504

You can use perform selector as below:

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
    _ = NSThread.init(target: myObj, selector:Selector("myFunc"),

        object: nil)
}

To perform some task in background you can use dispatcher as an alternative for performSelectorInBackground.

let backgroundQueue = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
    dispatch_async(backgroundQueue) { () -> Void in

        self.myFunc()

    }

Upvotes: 0

davecom
davecom

Reputation: 1498

A Selector is associated with the name of a method represented as a String. You're not properly initializing the Selector. Selector has an initializer that takes a String, so you shouldn't be passing it myObj.myFunc(). Instead you should be passing it "myFunc". See this question for more detail: @selector() in Swift?

Upvotes: 1

Related Questions