swift 3 DispatchGroup leave causes crash when called in helper class function

user_8395316 0
Viewed 11850

I'm using DispatchGroup.enter() and leave() to process a helper class's reverseG async function. Problem is clear, I'm using mainViewController's object to call mainViewControllers's dispatchGroup.leave() in helper class! Is there a way to do it?

Same code works when reverseG is declared in the main view controller.

class Geo {
    var obj = ViewController()

    static func reverseG(_ coordinates: CLLocation, _ completion: @escaping (CLPlacemark) -> ()) {
        let geoCoder = CLGeocoder()
        geoCoder.reverseGeocodeLocation(coordinates) { (placemarks, error) in
            if let error = error {
                print("error: \(error.localizedDescription)")
            }
            if let placemarks = placemarks, placemarks.count > 0 {
                let placemark = placemarks.first!
                completion(placemark) // set ViewController's properties
            } else {
                print("no data")
            }
            obj.dispatchGroup.leave() // ** ERROR **
        }
    }


}

Function call from main view controller

dispatchGroup.enter()
Geo.reverseG(coordinates, setValues) // completionHandler: setValues

dispatchGroup.notify(queue: DispatchQueue.main) {

    // call another function on completion

}
completionhandler grand-central-dispatch reverse-geocoding swift
3 Answers

my two cents to show how can work: (maybe useful for others..)

//  Created by ing.conti on 02/02/21.
//

import Foundation

print("Hello, World!")
let r = AsyncRunner()
r.runMultiple(args: ["Sam", "Sarah", "Tom"])





class AsyncRunner{
    static let shared = AsyncRunner()
    
    let dispatchQueue = DispatchQueue(label: "MyQueue", qos:.userInitiated)
    let dispatchGroup = DispatchGroup.init()
    
    
    func runMultiple(args: [String]){
        
        let count = args.count
        
        for i in 0..<count {
            
            dispatchQueue.async(group: dispatchGroup) { [unowned self] in
                dispatchGroup.enter()
                self.fakeTask(arg: args[i])
            }
        }
        
        _ = dispatchGroup.wait(timeout: DispatchTime.distantFuture)
    }
    
    
    
    func fakeTask(arg: String){
        
        for i in 0..<3 {
            print(arg, i)
            sleep(1)
        }
        dispatchGroup.leave()
    }    
}
user_9273330
Related