TaskChain DataFlex Reference Documentation

TaskChain

Current Version: 10.1.2

Represents a chain of asynchronous tasks to be run in sequence in a background thread.

Object Creation

// (Dataflex programs use the 32-bit Chilkat ActiveX)
Handle hoTaskChain
Get Create(RefClass(cComChilkatTaskChain)) to hoTaskChain

Properties

DebugLogFilePath
Function ComDebugLogFilePath Returns String
Procedure Set ComDebugLogFilePath String value

If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.

Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.

Possible causes of hangs include:

  • A timeout property set to 0, indicating an infinite timeout.
  • A hang occurring within an event callback in the application code.
  • An internal bug in the Chilkat code causing the hang.

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Finished
Function ComFinished Returns Boolean
Introduced in version 9.5.0.52

True if the task status is "canceled", "aborted", or "completed". A task chain can only reach the "canceled" status if it was activated via the Run method, made it onto the internal thread pool thread's queue, was waiting for a pool thread to become available, and was then canceled prior to the task actually starting.

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Inert
Function ComInert Returns Boolean
Introduced in version 9.5.0.52

True if the task status is "empty" or "loaded". When a task chain is inert, it has been loaded but is not scheduled to run yet.

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LastBinaryResult
Function ComLastBinaryResult Returns Variant

This property is mainly used in SQL Server stored procedures to retrieve binary data from the last method call that returned binary data. It is only accessible if Chilkat.Global.KeepBinaryResult is set to True. This feature allows for the retrieval of large varbinary results in an SQL Server environment, which has restrictions on returning large data via method calls, though temp tables can handle binary properties.

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LastErrorHtml
Function ComLastErrorHtml Returns String

Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorText
Function ComLastErrorText Returns String

Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastErrorXml
Function ComLastErrorXml Returns String

Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.

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LastMethodSuccess
Function ComLastMethodSuccess Returns Boolean
Procedure Set ComLastMethodSuccess Boolean value

Indicates the success or failure of the most recent method call: True means success, False means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages.

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LastStringResult
Function ComLastStringResult Returns String

In SQL Server stored procedures, this property holds the string return value of the most recent method call that returns a string. It is accessible only when Chilkat.Global.KeepStringResult is set to TRUE. SQL Server has limitations on string lengths returned from methods and properties, but temp tables can be used to access large strings.

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LastStringResultLen
Function ComLastStringResultLen Returns Integer

The length, in characters, of the string contained in the LastStringResult property.

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Live
Function ComLive Returns Boolean
Introduced in version 9.5.0.52

True if the task status is "queued" or "running". When a task chain is live, it is either already running, or is on the thread pool thread's queue waiting for a thread to become available.

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NumTasks
Function ComNumTasks Returns Integer
Introduced in version 9.5.0.52

The number of tasks contained within the task chain.

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Status
Function ComStatus Returns String
Introduced in version 9.5.0.52

The current status of the task chain. Possible values are:

  • "empty" -- No tasks have yet been appended to the task chain.
  • "loaded" -- The task chain has been loaded (appended) with one or more task objects.
  • "queued" -- The task chain is in the thread pool's queue of tasks awaiting to be run.
  • "running" -- The task chain is currently running.
  • "canceled" -- The task chain was canceled before it entered the "running" state.
  • "aborted" -- The task chain was canceled while it was in the running state.
  • "completed" -- The task chain completed.

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StatusInt
Function ComStatusInt Returns Integer
Introduced in version 9.5.0.52

The current status of the task as an integer value. Possible values are:

  • 1 -- "empty" -- No tasks have yet been appended to the task chain.
  • 2 -- "loaded" -- The task chain has been loaded (appended) with one or more task objects.
  • 3 -- "queued" -- The task chain is in the thread pool's queue of tasks awaiting to be run.
  • 4 -- "running" -- The task chain is currently running.
  • 5 -- "canceled" -- The task chain was canceled before it entered the "running" state.
  • 6 -- "aborted" -- The task chain was canceled while it was in the running state.
  • 7 -- "completed" -- The task chain completed.

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StopOnFailedTask
Function ComStopOnFailedTask Returns Boolean
Procedure Set ComStopOnFailedTask Boolean value
Introduced in version 9.5.0.52

If True then stops execution of the task chain if any individual task fails. Task failure is defined by the standard LastMethodSuccess property. If False, then all of the tasks in the chain will be run even if some fail. The default value of this property is True.

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VerboseLogging
Function ComVerboseLogging Returns Boolean
Procedure Set ComVerboseLogging Boolean value

If set to True, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
Function ComVersion Returns String

Version of the component/library, such as "10.1.0"

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Methods

Append
Function ComAppend cComChilkatTask task Returns Boolean
Introduced in version 9.5.0.52

Appends a task to the task chain. Can fail if the task is already part of another chain. (A task can only be part of a single chain.)

Returns True for success, False for failure.

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Cancel
Function ComCancel Returns Boolean
Introduced in version 9.5.0.52

Cancels execution of the asynchronous task chain.

Returns True for success, False for failure.

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GetTask
Function ComGetTask Integer index Returns cComChilkatTask
Introduced in version 9.5.0.52

Returns the Nth task in the chain. The 1st task is at index 0.

Returns null on failure

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Run
Function ComRun Returns Boolean
Introduced in version 9.5.0.52

Queues the task chain to run on the internal Chilkat thread pool. Each task in the chain will run, one after the other.

Returns True for success, False for failure.

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RunSynchronously
Function ComRunSynchronously Returns Boolean
Introduced in version 9.5.0.52

Runs the task chain synchronously. Then this method returns after all the tasks in the chain have been run.

Returns True for success, False for failure.

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SleepMs
Procedure ComSleepMs Integer numMs
Introduced in version 9.5.0.52

Convenience method to force the calling thread to sleep for a number of milliseconds.

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Wait
Function ComWait Integer maxWaitMs Returns Boolean
Introduced in version 9.5.0.52

Waits for the task chain to complete. Returns when all of the tasks in the chain have completed, or after maxWaitMs milliseconds have elapsed. (A maxWaitMs value of 0 is to wait indefinitely.) Returns (False) if the task chain has not yet been started by calling the Run method, or if the maxWaitMs expired. If the task chain completed, was already completed, was canceled, or aborted, then this method returns True.

Returns True for success, False for failure.

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