Tcl

Async Task Chain

See more Async Examples

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

load ./chilkat.dll

set success 0

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

set success 0

set mailman [new_CkMailMan]

# Set the POP3 server's hostname
CkMailMan_put_MailHost $mailman "pop.example.com"

# Set the POP3 login/password and any other requirements..
CkMailMan_put_PopUsername $mailman "myLogin"
CkMailMan_put_PopPassword $mailman "myPassword"
CkMailMan_put_PopSsl $mailman 1
CkMailMan_put_MailPort $mailman 995

# Connect to the POP3 server:
set success [CkMailMan_Pop3BeginSession $mailman]
if {!$success} then {
    puts [CkMailMan_lastErrorText $mailman]
    delete_CkMailMan $mailman
    exit
}

# Get the number of messages in the mailbox.
set numMessages [CkMailMan_GetMailboxCount $mailman]
if {$numMessages == 0} then {
    puts "No email messages in the POP3 mailbox."
    delete_CkMailMan $mailman
    exit
}

set taskChain [new_CkTaskChain]

# Create async task objects to fetch each email message
# by its sequence number

# task is a CkTask

for {set i 1} {$i <= $numMessages} {incr i} {

    set task [CkMailMan_FetchByMsgnumAsync $mailman $i]
    if {[CkMailMan_get_LastMethodSuccess $mailman] == 0} then {
        puts [CkMailMan_lastErrorText $mailman]
        delete_CkMailMan $mailman
        delete_CkTaskChain $taskChain
        exit
    }

    # Append each task to the task chain.
    set success [CkTaskChain_Append $taskChain $task]
    if {!$success} then {
        puts [CkTaskChain_lastErrorText $taskChain]
        delete_CkMailMan $mailman
        delete_CkTaskChain $taskChain
        exit
    }

    delete_CkTask $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.
CkTaskChain_put_StopOnFailedTask $taskChain 1
set success [CkTaskChain_Run $taskChain]
if {!$success} then {
    puts [CkTaskChain_lastErrorText $taskChain]
    delete_CkMailMan $mailman
    delete_CkTaskChain $taskChain
    exit
}

# 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 {[CkTaskChain_get_Finished $taskChain] != 1} {

    # Sleep 100 ms.
    CkTaskChain_SleepMs $taskChain 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 {[CkTaskChain_get_StatusInt $taskChain] != 7} then {
    puts "Task did not complete."
    puts "task chain status: [CkTaskChain_status $taskChain]"
    delete_CkMailMan $mailman
    delete_CkTaskChain $taskChain
    exit
}

set email [new_CkEmail]

set numTasks [CkTaskChain_get_NumTasks $taskChain]
set taskIdx 0

while {$taskIdx < $numTasks} {

    set task [CkTaskChain_GetTask $taskChain $taskIdx]

    # Load the email object with email downloaded by this task.
    set success [CkEmail_LoadTaskResult $email $task]
    if {!$success} then {
        puts "Failed to load email object for task."
    }     else {
        puts [CkEmail_from $email]; [CkEmail_subject $email]
    }

    delete_CkTask $task

    set taskIdx [expr $taskIdx + 1]
}

delete_CkMailMan $mailman
delete_CkTaskChain $taskChain
delete_CkEmail $email