QtTaskTree::Group Class

Detailed Description

Group is a container for other group items. It encloses child tasks into one unit, which is seen by the group's parent as a single, asynchronous task. Since Group is of the GroupItem type, it may also be a child of Group.

Insert child tasks into the group by using aliased custom task names, such as, QThreadFunctionTask<ResultType> or QNetworkReplyWrapperTask:

 const Group group {
     QNetworkReplyWrapperTask(...),
     QThreadFunctionTask<int>(...)
 };

You can customize the group's behavior by inserting the ExecutionMode or WorkflowPolicy items:

 const Group group {
     parallel,
     continueOnError,
     QNetworkReplyWrapperTask(...),
     QNetworkReplyWrapperTask(...)
 };

The group may contain nested groups:

 const Group group {
     finishAllAndSuccess,
     QNetworkReplyWrapperTask(...),
     Group {
         QNetworkReplyWrapperTask(...),
         Group {
             parallel,
             QNetworkReplyWrapperTask(...),
             QNetworkReplyWrapperTask(...),
         }
         QThreadFunctionTask<QString>(...)
     }
 };

The group may dynamically instantiate a custom storage structure, which may be used for inter-task data exchange:

 struct MyCustomStruct { QByteArray data; };

 Storage<MyCustomStruct> storage;

 const auto onFirstSetup = [](QNetworkReplyWrapper &task) { ... };
 const auto onFirstDone = [storage](const QNetworkReplyWrapper &task) {
     // storage-> gives a pointer to MyCustomStruct instance,
     // created dynamically by the running task tree.
     storage->data = task.reply()->readAll();
 };
 const auto onSecondSetup = [storage](QThreadFunction<QImage> &task) {
     // storage-> gives a pointer to MyCustomStruct. Since the group is sequential,
     // the stored MyCustomStruct was already updated inside the onFirstDone handler.
     const QByteArray storedData = storage->data;
 };

 const Group group {
     // When the group is entered by a running task tree, it creates MyCustomStruct
     // instance dynamically. It is later accessible from all handlers via
     // the *storage or storage-> operators.
     sequential,
     storage,
     QNetworkReplyWrapperTask(onFirstSetup, onFirstDone, CallDone::OnSuccess),
     QThreadFunctionTask<QImage>(onSecondSetup)
 };