Visual Basic 6.0

Async Methods Returning an Object

See more Async Examples

Demonstrates how to call an asynchronous method that returns an object. This example reads email from a POP3 server using the Async versions of the Chilkat methods. Visual Basic 6.0

Dim success As Long
success = 0

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

success = 0

Dim mailman As New ChilkatMailMan

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

' Set the POP3 login/password and any other requirements..
mailman.PopUsername = "myLogin"
mailman.PopPassword = "myPassword"
mailman.PopSsl = 1
mailman.MailPort = 995

' Connect to the POP3 server:
Dim task As ChilkatTask
Set task = mailman.Pop3BeginSessionAsync()
If (mailman.LastMethodSuccess = 0) Then
    Debug.Print mailman.LastErrorText
    Exit Sub
End If

' Start the background task.
success = task.Run()
If (Not success) Then
    Debug.Print task.LastErrorText

    Exit Sub
End If

' Wait for the POP3 connect task to finish.
' The 1/0 returned by Wait applies to the Wait method call, not the task.
Dim maxWaitMs As Long
maxWaitMs = 30000
success = task.Wait(maxWaitMs)
If (Not success Or (task.StatusInt <> 7) Or (task.TaskSuccess <> 1)) Then
    If (Not success) Then
        ' The task.LastErrorText applies to the Wait method call.
        Debug.Print task.LastErrorText
    Else
        ' The ResultErrorText applies to the underlying task method call (i.e. the Pop3BeginSession)
        Debug.Print task.Status
        Debug.Print task.ResultErrorText
    End If

    Exit Sub
End If

' Get the number of messages in the mailbox.
Set task = mailman.GetMailboxCountAsync()

' To keep the example short, we'll skip handling failures.
' The failures would be handled in the same way as shown above.

success = task.Run()
success = task.Wait(maxWaitMs)
Dim numMessages As Long
numMessages = task.GetResultInt()

If (numMessages = 0) Then
    Exit Sub
End If

Dim email As New ChilkatEmail

Dim i As Long
For i = 1 To numMessages

    Set task = mailman.FetchByMsgnumAsync(i)
    If (mailman.LastMethodSuccess = 0) Then
        Debug.Print mailman.LastErrorText
        Exit Sub
    End If

    success = task.Run()
    success = task.Wait(maxWaitMs)
    If (Not success Or (task.StatusInt <> 7) Or (task.TaskSuccess <> 1)) Then
        If (Not success) Then
            ' The task.LastErrorText applies to the Wait method call.
            Debug.Print task.LastErrorText
        Else
            ' The ResultErrorText applies to the underlying task method call (i.e. the FetchByMsgnum)
            Debug.Print task.Status
            Debug.Print task.ResultErrorText
        End If

        Exit Sub
    End If

    ' Each Chilkat object that can be a return value of an asynchronous task will
    ' have a method named LoadTaskResult.  The object returned in the underlying
    ' asynchronous method call is retrieved by calling LoadTaskResult. 

    ' To say it another way: The application will provide a pre-existing object of
    ' the desired return type (in this case it is an email object).  This object is
    ' loaded by calling LoadTaskResult.  

    success = email.LoadTaskResult(task)

    If (Not success) Then
        Debug.Print email.LastErrorText
        Exit Sub
    Else
        Debug.Print email.From & ": " & email.Subject & vbLf
    End If

Next