12.4 - Deriving a New Task from DtSimTask

If you want to derive a new task from DtSimTask, you have to complete the following general steps:

1. Derive the new task from DtSimTask.
2. Implement DtSimTask functions for the task.
3. Register the task with the task factory.
4. Add a controller for the task.
5. Extract task data from the task message.

The first step in creating a new task type is to create a new task class derived from DtSimTask. You need to assign it a unique integer type to identify the task (task type names are defined in radioMsgTypes.h). The entity’s controllers use the task type to determine how to handle an incoming task.

The DtSimTask class has the following pure virtual member functions that you must override in the derived task:

• The type() member function returns a unique integer identifying the class type.
• The clone() member function must return a pointer to a newly created instance of the derived class.
• You must implement the string representation function (stringRep()) to return a human-readable character string representation of the task for use in the plan editor and viewer.
• You must implement a static creator function for use by the task factory.

To make your new DtSimTask capable of being sent over the network, as part of a DtTaskMessage or as part of a DtIfPlan message, you must override the following member functions in your derived task:

• The netRepSize() member function returns the size in bytes of the network representation of the task
• The sendToNet() member function writes the member data of the class to a buffer in a form suitable for transmitting over a network in a platform-independent manner
• The setFromNet() member function takes an incoming buffer from a network message and sets the class member data from the network representation.

Once you have defined a new task and have registered the task with the factory, add a new controller to the simulation object to carry out the action described by the task. To do this, you must derive a new controller from DtTaskControllerComponent. (For details, please see 5.2.7 Controller Components.) The new controller must have a unique string type and must be registered with the corresponding component factory.

In your new task controller component, you must override registerTaskMsgCallbacks() to register your callback function for handling the new task. Once it is registered, your callback function will be called when a message of the new derived type is received on its radio net. In your callback (actually, in a virtual member function of your controller, called from the static callback), extract the necessary data from the task message parameters and start executing the task.

The addTaskSim example demonstrates how to add a new kind of DtSimTask to the back-end.

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