(Swift 2) Async Task Chain

Demonstrates how to combine a sequence of asynchronous tasks into a single task chain to be run in a background thread.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // All Chilkat classes can be unlocked at once at the beginning of a program
    // by calling UnlockBundle.  It requires a Bundle unlock code.
    let chilkatGlob = CkoGlobal()
    var success: Bool = chilkatGlob.UnlockBundle("Anything for 30-day trial.")
    if success != true {
        print("\(chilkatGlob.LastErrorText)")
        return
    }

    let mailman = CkoMailMan()

    // Set the POP3 server's hostname
    mailman.MailHost = "pop.someMailServer.com"

    // Set the POP3 login/password and any other requirements..
    mailman.PopUsername = "myLogin"
    mailman.PopPassword = "myPassword"
    mailman.PopSsl = true
    mailman.MailPort = 995

    // Connect to the POP3 server:
    success = mailman.Pop3BeginSession()
    if !success {
        print("\(mailman.LastErrorText)")
        return
    }

    // Get the number of messages in the mailbox.
    var numMessages: Int = mailman.GetMailboxCount().intValue
    if numMessages == 0 {
        print("No email messages in the POP3 mailbox.")
        return
    }

    let taskChain = CkoTaskChain()

    // Create async task objects to fetch each email message
    // by its sequence number
    var i: Int
    var task: CkoTask?

    for i = 1; i <= numMessages; i++ {

        task = mailman.FetchByMsgnumAsync(i)
        if mailman.LastMethodSuccess == false {
            print("\(mailman.LastErrorText)")
            return
        }

        // Append each task to the task chain.
        success = taskChain.Append(task)
        if !success {
            print("\(taskChain.LastErrorText)")
            return
        }

        task = nil

    }

    // At this point, no tasks have actually started running.
    // All we've done so far is to create tasks for the work that will be done
    // when the task chain is run.

    // Start the task chain running in a background thread.
    // Each task is run one after the other (on the same background thread) until all tasks have completed.
    // The task chain will stop at the first task that fails.
    taskChain.StopOnFailedTask = true
    success = taskChain.Run()
    if !success {
        print("\(taskChain.LastErrorText)")
        return
    }

    // The application is now free to do anything else
    // while the emails are being downloaded

    // For this example, we'll simply sleep and periodically
    // check to see if the taskchain if finished. 
    while taskChain.Finished != true {

        // Sleep 100 ms.
        taskChain.SleepMs(100)

    }

    // A finished task chain could be one that was canceled, aborted, or truly finished.  

    // If the task chain "completed", then it ran to completion.  A "completed" task will
    // have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
    // been aborted or canceled:
    if taskChain.StatusInt.intValue != 7 {
        print("Task did not complete.")
        print("task chain status: \(taskChain.Status)")
        return
    }

    let email = CkoEmail()

    var numTasks: Int = taskChain.NumTasks.intValue
    var taskIdx: Int = 0

    while (taskIdx < numTasks) {

        task = taskChain.GetTask(taskIdx)

        // Load the email object with email downloaded by this task.
        success = email.LoadTaskResult(task)
        if !success {
            print("Failed to load email object for task.")
        }
        else {
            print("\(email.From); \(email.Subject)")
        }

        task = nil

        taskIdx = taskIdx + 1
    }


}