TaskChain Delphi DLL Reference Documentation

TaskChain

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

Create/Dispose

function CkTaskChain_Create: HCkTaskChain; stdcall;

Creates an instance of the HCkTaskChain object and returns a handle (i.e. a Pointer). The handle is passed in the 1st argument for the functions listed on this page.

procedure CkTaskChain_Dispose(handle: HCkTaskChain); stdcall;

Objects created by calling CkTaskChain_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function.

Properties

procedure CkTaskChain_getDebugLogFilePath(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;
procedure CkTaskChain_putDebugLogFilePath(objHandle: HCkTaskChain; newPropVal: PWideChar); stdcall;

function CkTaskChain__debugLogFilePath(objHandle: HCkTaskChain): PWideChar; stdcall;

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.

function CkTaskChain_getFinished(objHandle: HCkTaskChain): wordbool; stdcall;

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.

function CkTaskChain_getInert(objHandle: HCkTaskChain): wordbool; stdcall;

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.

procedure CkTaskChain_getLastErrorHtml(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;

function CkTaskChain__lastErrorHtml(objHandle: HCkTaskChain): PWideChar; stdcall;

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.

procedure CkTaskChain_getLastErrorText(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;

function CkTaskChain__lastErrorText(objHandle: HCkTaskChain): PWideChar; stdcall;

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.

Concept of LastErrorText

LastErrorText Standard Information

procedure CkTaskChain_getLastErrorXml(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;

function CkTaskChain__lastErrorXml(objHandle: HCkTaskChain): PWideChar; stdcall;

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.

function CkTaskChain_getLastMethodSuccess(objHandle: HCkTaskChain): wordbool; stdcall;
procedure CkTaskChain_putLastMethodSuccess(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;

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.

function CkTaskChain_getLive(objHandle: HCkTaskChain): wordbool; stdcall;

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.

function CkTaskChain_getNumTasks(objHandle: HCkTaskChain): Integer; stdcall;

Introduced in version 9.5.0.52

The number of tasks contained within the task chain.

procedure CkTaskChain_getStatus(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;

function CkTaskChain__status(objHandle: HCkTaskChain): PWideChar; stdcall;

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.

function CkTaskChain_getStatusInt(objHandle: HCkTaskChain): Integer; stdcall;

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.

function CkTaskChain_getStopOnFailedTask(objHandle: HCkTaskChain): wordbool; stdcall;
procedure CkTaskChain_putStopOnFailedTask(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;

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.

Async Methods Returning an Object

function CkTaskChain_getVerboseLogging(objHandle: HCkTaskChain): wordbool; stdcall;
procedure CkTaskChain_putVerboseLogging(objHandle: HCkTaskChain; newPropVal: wordbool); stdcall;

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.

procedure CkTaskChain_getVersion(objHandle: HCkTaskChain; outPropVal: HCkString); stdcall;

function CkTaskChain__version(objHandle: HCkTaskChain): PWideChar; stdcall;

Version of the component/library, such as "9.5.0.63"

Methods

function CkTaskChain_Append(objHandle: HCkTaskChain;
    task: HCkTask): wordbool; stdcall;

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.

Async Task Chain

function CkTaskChain_Cancel(objHandle: HCkTaskChain): wordbool; stdcall;

Introduced in version 9.5.0.52

Cancels execution of the asynchronous task chain.

Returns True for success, False for failure.

function CkTaskChain_GetTask(objHandle: HCkTaskChain;
    index: Integer): HCkTask; stdcall;

Introduced in version 9.5.0.52

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

Returns nil on failure

Async Methods Returning an Object

function CkTaskChain_Run(objHandle: HCkTaskChain): wordbool; stdcall;

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.

function CkTaskChain_RunSynchronously(objHandle: HCkTaskChain): wordbool; stdcall;

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.

function CkTaskChain_SaveLastError(objHandle: HCkTaskChain;
    path: PWideChar): wordbool; stdcall;

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns True for success, False for failure.

procedure CkTaskChain_SleepMs(objHandle: HCkTaskChain;
    numMs: Integer) stdcall;

Introduced in version 9.5.0.52

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

function CkTaskChain_Wait(objHandle: HCkTaskChain;
    maxWaitMs: Integer): wordbool; stdcall;

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.