(MFC) 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 C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkGlobal.h>
#include <CkMailMan.h>
#include <CkTaskChain.h>
#include <CkTask.h>
#include <CkEmail.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // All Chilkat classes can be unlocked at once at the beginning of a program
    // by calling UnlockBundle.  It requires a Bundle unlock code.
    CkGlobal chilkatGlob;
    bool success = chilkatGlob.UnlockBundle("Anything for 30-day trial.");
    if (success != true) {
        strOut.append(chilkatGlob.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkMailMan mailman;

    // Set the POP3 server's hostname
    mailman.put_MailHost("pop.someMailServer.com");

    // Set the POP3 login/password and any other requirements..
    mailman.put_PopUsername("myLogin");
    mailman.put_PopPassword("myPassword");
    mailman.put_PopSsl(true);
    mailman.put_MailPort(995);

    // Connect to the POP3 server:
    success = mailman.Pop3BeginSession();
    if (!success) {
        strOut.append(mailman.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Get the number of messages in the mailbox.
    int numMessages = mailman.GetMailboxCount();
    if (numMessages == 0) {
        strOut.append("No email messages in the POP3 mailbox.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkTaskChain taskChain;

    // Create async task objects to fetch each email message
    // by its sequence number
    int i;
    CkTask *task = 0;

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

        task = mailman.FetchByMsgnumAsync(i);
        if (mailman.get_LastMethodSuccess() == false) {
            strOut.append(mailman.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        // Append each task to the task chain.
        success = taskChain.Append(*task);
        if (!success) {
            strOut.append(taskChain.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        delete task;

    }

    // 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.put_StopOnFailedTask(true);
    success = taskChain.Run();
    if (!success) {
        strOut.append(taskChain.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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.get_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.get_StatusInt() != 7) {
        strOut.append("Task did not complete.");
        strOut.append("\r\n");
        strOut.append("task chain status: ");
        strOut.append(taskChain.status());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkEmail email;

    int numTasks = taskChain.get_NumTasks();
    int taskIdx = 0;

    while ((taskIdx < numTasks)) {

        task = taskChain.GetTask(taskIdx);

        // Load the email object with email downloaded by this task.
        success = email.LoadTaskResult(*task);
        if (!success) {
            strOut.append("Failed to load email object for task.");
            strOut.append("\r\n");
        }
        else {
            strOut.append(email.ck_from());
            strOut.append("; ");
            strOut.append(email.subject());
            strOut.append("\r\n");
        }

        delete task;

        taskIdx = taskIdx + 1;
    }



    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }