Swift

Cancel Async Task if not Completed after a Max Time

See more Async Examples

Demonstrates how to wait a maximum amount of time for an asynchronous task to completed. If not completed in the allotted amount of time, the task is cancelled. Swift

func chilkatTest() {
    var success: Bool = false

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let http = CkoHttp()!

    // Set some timeouts, in seconds:
    http.connectTimeout = 15
    http.readTimeout = 15

    // Wait a max time of 2 seconds for the task.
    // In this example, it's an unreasonably small amount of time,
    // which means the task will get cancelled.
    var waitMaxMs: Int = 2000

    // We're just going to download for 2 seconds and then cancel.
    // Substitute your own URL with a large enough file for testing..
    var downloadUrl: String? = "http://download.mono-project.com/archive/4.6.1/windows-installer/mono-4.6.1.5-gtksharp-2.12.38-win32-0.msi"

    var task: CkoTask? = http.downloadAsync(url: downloadUrl, saveToPath: "qa_output/mono.msi")
    task!.run()

    // Wait a maximum of waitMaxMs for the task (i.e. the HTTP download) to complete.
    // The Wait method returns when the task has been canceled, aborted, or completed, or when the max allotted time has passed.
    task!.wait(maxWaitMs: waitMaxMs)

    // At this point, the download may or may not have completed.  
    // Rather than checking the Task status, we can call task.Cancel because
    // if the Task is no longer running (because it already completed, was canceled or aborted), then the 
    // call to Cancel is a NO-OP (meaning it does nothing and the Task's status is unaffected).
    // Also, task.Cancel returns true if the task was in the "queued" or "running" state and was canceled or aborted. 
    // The method returns false if the task has any other status.
    var wasCanceled: Bool = task!.cancel()
    if wasCanceled == true {
        print("The HTTP download took too long and was canceled.")
    }
    else {
        // Find out what happened.
        if task!.statusInt.intValue == 7 {
            // The task completed, which means the background thread's call to Download completed
            // with success or failure.  Find out which...
            success = task!.getResultBool()
            if success == true {
                print("Download successful!")
            }
            else {
                print("Download failed prior to waitMaxMs...")
                print("\(task!.resultErrorText!)")
            }

        }
        else {
            // The task must've been canceled or aborted by some other means..
            print("Task did not complete.  Final status: \(task!.status!)")
        }

    }

    task = nil

}