The 'Signal' method

Argument: Any
Result: None

Valid for: System and APL (child task) object

The Signal method allows the child task to send a message to the parent, and vice versa. It is used in conjunction with the onSignal event, as follows:

• If the parent wants to send a signal to the child, it invokes the Signal method in the APL (child task) object. This causes an onSignal event to trigger in the System object of the child task.

• Conversely, if the child task wishes to send a signal to the parent, it invokes the Signal method in its own System object. This causes an onSignal event to trigger in the APL (child task) object of the parent.

In both cases, the Signal method optionally takes an argument, which can be any APL array (or an APLX overlay created using ⎕OV). This is typically used to send a command to the other task, or to return a result to it. Any argument to the Signal method is available to the receiving task as the ⎕WARG system variable during the execution of the callback.

See the section on APLX Multi-tasking for more details.