TaskChain DataFlex Reference Documentation

TaskChain

Current Version: 9.5.0.73

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, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes 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
Introduced in version 9.5.0.52

The binary data returned by the last (binary data returning) method called. Only available if Chilkat.Global.KeepBinaryResult is set to True. This provides a means for obtaining large varbinary results in the SQL Server environment (where limitations exist in getting large amounts of data returned by method calls, but where temp tables can be used for binary properties).

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LastErrorHtml
Function ComLastErrorHtml Returns String

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorText
Function ComLastErrorText Returns String

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorXml
Function ComLastErrorXml Returns String

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastMethodSuccess
Function ComLastMethodSuccess Returns Boolean
Procedure Set ComLastMethodSuccess Boolean value
Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of True indicates success, a value of False indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = True and failure = False.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to True. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

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LastStringResult
Function ComLastStringResult Returns String
Introduced in version 9.5.0.52

The string return value of the last (string returning) method called. Only available if Chilkat.Global.KeepStringResult is set to True. This provides a means for obtaining large string results in the SQL Server environment (where limitations exist in getting long strings returned by method calls, but where temp tables can be used for string properties).

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LastStringResultLen
Function ComLastStringResultLen Returns Integer
Introduced in version 9.5.0.53

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.

More Information and Examples
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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 "9.5.0.63"

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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.

More Information and Examples
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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

More Information and Examples
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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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