Swift Post Concurrency Blog Post Code Example

Concurrency3.swift

class FetchRestaurantInventoryOperation: Operation {
    var restaurantData: RestaurantData
    var networkProvider: NetworkProvider
    
    // 1
    private var _executing = false {
        willSet {
            willChangeValue(forKey: "isExecuting")
        }
        didSet {
            didChangeValue(forKey: "isExecuting")
        }
    }
    
    // 1
    private var _finished = false {
        willSet {
            willChangeValue(forKey: "isFinished")
        }
        
        didSet {
            didChangeValue(forKey: "isFinished")
        }
    }
    
    
    init(restaurantData: RestaurantData, networkProvider: NetworkProvider) {
        self.restaurantData = restaurantData
        self.networkProvider = networkProvider
    }
    
    // 2
    override func main() {
        if isCancelled {
            self.finish(true)
            return
        }
        
        self.executing(true)
        self.networkProvider.fetchInventory() { jsonData in
            if let json = jsonData, !json.isEmpty {
                guard let serializedDictionary = try? JSONSerialization.jsonObject(with: json, options: []) as? [String: Any] else { return }
                self.restaurantData.setInventoryJSON(serializedDictionary)
                self.restaurantData.state = .downloaded
            } else {
                self.restaurantData.state = .failed
            }
            self.executing(false)
            self.finish(true)
        }
    }

    // 2
    override var isExecuting: Bool {
        return _executing
    }
    
    // 2
    override var isAsynchronous: Bool {
        return true
    }
    
    // 2
    override var isFinished: Bool {
        return _finished
    }
    
    // Helper methods
    func executing(_ executing: Bool) {
        _executing = executing
    }
    
    func finish(_ finished: Bool) {
        _finished = finished
    }
}