5.3 Defining the callbacks

5.3.5 Exiting the task list manager

The exit-task method allows you to exit the task list manager. It is invoked by choosing File > Exit. The definition of this method is quite simple.

define method exit-task (gadget :: <gadget>) => ()
  let frame = sheet-frame(gadget);
  let task-list = frame-task-list(frame);
  save-file (gadget);
  exit-frame(frame)
end method exit-task;

Add this method to the file frame.dylan.

The method takes the gadget used to invoke it and returns no values. In this case, exit-task is only ever invoked by the exit-menu-button gadget.

As with many other callbacks in this example, exit-task sets a number of local variables:

frame: The frame that the gadget argument belongs to.
task-list: The task list associated with frame.

The method begins by calling the save-file method (defined in Section 5.3.1.2) to save the current task list to disk. This ensures that the user does not lose any work. Next, the exit-frame generic function is invoked to exit the task list manager window.