TaskChain Objective-C Reference Documentation
CkoTaskChain
Current Version: 10.1.2
Represents a chain of asynchronous tasks to be run in sequence in a background thread.
Object Creation
CkoTaskChain *obj = [[CkoTaskChain alloc] init];
Properties
DebugLogFilePath
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.
Finished
YES 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.
topHeartbeatMs
The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort the Wait method. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire. Note: An asynchronous task chain running in a background thread (in one of the thread pool threads) does not fire events. The task chain's event callbacks pertain only to the Wait method.
topInert
YES 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.
topLastErrorHtml
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.
topLastErrorText
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.
LastErrorXml
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.
topLastMethodSuccess
Indicates the success or failure of the most recent method call: YES means success, NO 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.
topLive
YES 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.
topNumTasks
The number of tasks contained within the task chain.
topStatus
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.
StatusInt
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.
StopOnFailedTask
If YES then stops execution of the task chain if any individual task fails. Task failure is defined by the standard LastMethodSuccess property. If NO, then all of the tasks in the chain will be run even if some fail. The default value of this property is YES.
VerboseLogging
If set to YES, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is NO. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
topVersion
Methods
Append
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 YES for success, NO for failure.
Cancel
GetTask
Returns the Nth task in the chain. The 1st task is at index 0.
Returns nil on failure
Run
Queues the task chain to run on the internal Chilkat thread pool. Each task in the chain will run, one after the other.
Returns YES for success, NO for failure.
topRunSynchronously
Runs the task chain synchronously. Then this method returns after all the tasks in the chain have been run.
Returns YES for success, NO for failure.
topSleepMs
Convenience method to force the calling thread to sleep for a number of milliseconds.
topWait
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 (NO) 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 YES.
Returns YES for success, NO for failure.
topEvents
To implement an event callback, your application would define and implement a class that inherits from CkoBaseProgress. Your application can implement methods to override some or all of the default/empty method implementations of the CkoBaseProgress base class.
For example:
CkoTaskChain *taskchain = [[CkoTaskChain alloc] init]; MyTaskChainProgress *callbackObj = [[MyTaskChainProgress alloc] init]; [taskchain setEventCallbackObject:callbackObj];
MyTaskChainProgress interface example:
#import "CkoTaskChainProgress.h"
@interface MyTaskChainProgress : CkoBaseProgress {
}
- (id)init;
- (void)dealloc;
- (void)dispose;
- (void)AbortCheck:(BOOL *)abort;
- (void)PercentDone:(NSNumber *)pctDone
abort:(BOOL *)abort;
- (void)ProgressInfo:(NSString *)name
value:(NSString *)value;
- (void)TaskCompleted:(CkoTask *)task;
@endAbortCheck
Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200.
PercentDone
abort:(BOOL *)abort;
Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).
The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.
The abort output argument provides a means for aborting the operation. Setting it to YES will cause the method to abort and return a failed status (or whatever return value indicates failure).
ProgressInfo
value:(NSString *)value;
A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.
TaskCompleted
Called in the background thread when an asynchronous task completes.