olbrichj

fetchPromise().then { value in
  // do something
}.catch { error in {
  // in case of error  
}

olbrichj

Promise() { fulfill, reject in
    return "Hello World" //or other async code           
}

olbrichj

Promise() { fulfill, reject in
    // code       
}

olbrichj

class NetworkOperation: Operation {
    var targetURL: String?
    var resultData: Data?
    var _finished = false
    override var isFinished: Bool {
        get {
            return _finished
        }
        set (newValue) {
            willChangeValue(for: \.isFinished)

olbrichj

public class ApiRequestDelegate:NSObject, URLSessionDelegate, URLSessionTaskDelegate,
URLSessionDataDelegate{
    
    // called once as soon as a response returns
    public func urlSession(session: URLSession, dataTask: URLSessionDataTask,
                           didReceiveResponse response: URLResponse,
                           completionHandler: (URLSession.ResponseDisposition) -> Void) {
        // store Response to further process it and call completion Handler to continue
    }
    

olbrichj

URLSession.shared.dataTask(with: backendurl!) { data, _, error in
    if error != nil {
        print(error)
        return
    }
    
    let imageurl = String(data: data!, encoding: String.Encoding.utf8) as String! // For simplicity response is only the URL
    URLSession.shared.dataTask(with: URL(string:imageurl!)!) { (data, response, error) in
        if error != nil {
            print(error)

olbrichj

URLSession.shared.dataTask(with: url!) { data, _, error in
    if error != nil {
        print(error)
        return
    }
    DispatchQueue.main.async {
        imageView.image = UIImage(data: data!)
    }
}.resume()

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let op1 = Operation()
op1.name = "Operation1"

OperationQueue.main.addOperations([op1], waitUntilFinished:false)
let operations = OperationQueue.main.operations

operations.map { op in
    if op.name == "Operation1" {
        op.cancel()
    }

olbrichj

import Foundation

class UIOperation: AsyncOperation {
    let viewController: UIViewcontroller!
  
    override func execute() {
        let alert = UIAlertController(title: "My Alert", message: @"This is an alert.", preferredStyle: .alert) 
        alert.addAction(UIAlertAction(title: "OK", style: .`default`, handler: { _ in 
              self.handleInput()
        }))

olbrichj

class GroupOperation: AsyncOperation {
    let queue = OperationQueue()
    var operations: [AsyncOperation] = []
    var errors: [Error] = []
    
    override func execute() {
        print("group started")
        queue.addOperations(operations, waitUntilFinished: true)
        print("group done")
    }