Tasks v0.3.0

Tasks in v0.3.0

fwk::EventTask and fwk::HttpTask were removed from the framework (they were only used internally anyway). The API to use both fwk::EventHandle and fwk::HttpRequest remains unchanged.

API changes

To create fwk::SimpleTask and fwk::PeriodicTask you must give a key as first parameter. It is of type const void *, and can be set to nullptr if you don't need it.

This key parameter will be useful to purge the task queue of tasks you wan't to delete before they are executed (for example, if the task captured an object that is being destroyed, you can purge the task queue to avoid accessing an invalid memory address).

Examples

Creating a fwk::SimpleTask is the same as before, with a key as first parameter.

fwk::SimpleTask* task = fwk::SimpleTask::getFromPool(
    this, // the key, it can be a pointer to anything
    [] (void) -> void {
        // callback
    },
    [] (void) -> void {
        // cleanup
    });

fwk::WorkerManager::get().addTask(task);

// or

fwk::WorkerManager::get().addSimpleTask(
    this,
    [] (void) -> void {
        // callback
    },
    [] (void) -> void {
        // cleanup
    });

Same thing for the fwk::PeriodicTask.

fwk::PeriodicTask* periodicTask = fwk::PeriodicTask::getFromPool();

periodicTask->init(
    this, // the key, it can be a pointer to anything
    [&] (void) -> void {
        // stop executing the task at regular intervals.
        periodicTask->stop();
    },
    [] (void) -> void {
        // cleanup
    },
    std::chrono::seconds(5), // execute the callback every 5 seconds
    true); // start executing now (false = 1st execution in 5 seconds)

fwk::WorkerManager::get().addTask(periodicTask);

Callback changes

The cleanup callback of a fwk::SimpleTask will always be called, after the execution callback, and if the framework is shut down before the task is executed.

Purging the task queue

With this version, it is now possible to purge the task queue of any task that was added with a specific key (a const void* key). This key can be anything. If a nullptr key is given, you cannot purge the task queue.

Example

In this example, we create a fwk::PeriodicTask with this as key. The task will be executed the first time in 5 seconds.

Then we purge the task queue, meaning that the fwk::PeriodicTask will never be executed.

If you wan't to cancel the task, just use periodicTask->stop(), otherwise the cleanup callback will not be called.

Keep in mind that if you purge the task queue, the cleanup callback given to either fwk::SimpleTask or fwk::PeriodicTask will not be called. Be careful with this if you wan't to avoid leaks.

We create the task:

fwk::PeriodicTask* periodicTask = fwk::PeriodicTask::getFromPool();

periodicTask->init(
    this, // the key, it can be a pointer to anything
    [&] (void) -> void {
        // stop executing the task at regular intervals.
        periodicTask->stop();
    },
    [] (void) -> void {
        // cleanup
    },
    std::chrono::seconds(5), // execute the callback every 5 seconds
    false); // first execution in 5 seconds

fwk::WorkerManager::get().addTask(periodicTask);

We purge the task queue (asserting that we are in the same object and that the this key is the same).

fwk::WorkerManager::get().purgeTaskQueue(this);
// now the task is removed from the queue.