Xojo Plugin

Async Task Chain (another example)

See more Async Examples

Demonstrates using a task chain to run a sequence of FTP tasks asynchronously. Xojo Plugin

Dim success As Boolean
success = False

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

success = False

Dim ftp As New Chilkat.Ftp2

ftp.Hostname = "ftp.example.com"
ftp.Username = "login"
ftp.Password = "password"

// Connect and login to the FTP server.
success = ftp.Connect()
If (success <> True) Then
    System.DebugLog(ftp.LastErrorText)
    Return
End If

Dim taskChain As New Chilkat.TaskChain

// Create a task to change to the remote directory where the file will be uploaded.
Dim task As Chilkat.Task
task = ftp.ChangeRemoteDirAsync("junk")
If (ftp.LastMethodSuccess = False) Then
    System.DebugLog(ftp.LastErrorText)
    Return
End If

// Add this task to the task chain.
success = taskChain.Append(task)

// Create a task to upload a file.
Dim localFilename As String
localFilename = "c:/temp/hamlet.xml"
Dim remoteFilename As String
remoteFilename = "hamlet.xml"

task = ftp.PutFileAsync(localFilename,remoteFilename)
If (ftp.LastMethodSuccess = False) Then
    System.DebugLog(ftp.LastErrorText)
    Return
End If

// Add this task to the task chain.
success = taskChain.Append(task)

// 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 (Not success) Then
    System.DebugLog(taskChain.LastErrorText)
    Return
End If

// The application is now free to do anything else
// while the FTP commands are being run...

// 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

Wend

// 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 <> 7) Then
    System.DebugLog("Task did not complete.")
    System.DebugLog("task chain status: " + taskChain.Status)
    Return
End If

// If we got to this point, the ChangeRemoteDir and PutFile were successful.
// We can visually verify by examining the LastErrorText that was recorded for each
// of these method calls..
Dim numTasks As Int32
numTasks = taskChain.NumTasks
Dim taskIdx As Int32
taskIdx = 0

While (taskIdx < numTasks)

    task = taskChain.GetTask(taskIdx)

    // Examine the status of this task, and the ResultErrorText
    // (the ResultErrorText is the ftp.LastErrorText captured for FTP method called by the task).
    // Everything should indicate success.
    System.DebugLog("task status: " + task.Status)
    System.DebugLog("task log: " + task.ResultErrorText)

    taskIdx = taskIdx + 1
Wend

success = ftp.Disconnect()