TaskChain Objective-C Reference Documentation
CkoTaskChain
Current Version: 11.1.0
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.
HeartbeatMs
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.
LastErrorHtml
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.
Live
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.
NumTasks
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 therunningstate.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 therunningstate. - 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.
Version
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
Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.
PercentDone
abort:(BOOL *)abort;
This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).
The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.
To abort the operation, set the abort output argument to YES. This will cause the method to terminate and return a failure status or corresponding failure value.
ProgressInfo
value:(NSString *)value;
This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.
TaskCompleted
Called from the background thread when an asynchronous task completes.