Apple Newton Programmer’s Newton 2.0 (for Newton 2.0) - Manual (Page 633)

C H A P T E R 1 7
Additional System Services
Using Additional System Services 17-17
performing the myFunc function, pass it as the value of the workFunc parameter to
the DoProgress function, as illustrated in the following code fragment:
// options and data are accessible from workFunc because
// the workFunc "closes over" this context
myOpts := { wFnData:"Confabulating",
closebox:nil,
icon: kMyIcon,
statusText: kAppName,
gauge: 10,
titleText:"One moment, please."};
workFunc := func (theContextView)
begin
for x := 1 to 10 do
begin
myOpts.titleText:= :SomeWork(myOpts.wFnData);
myOpts.gauge := x * 10;
try
theContextView:SetStatus('vGauge,myOpts);
// handle any exceptions you anticipate
onexception |evt.ex.foo| do
// handle & possibly rethrow if it's fatal
onexception |evt.ex.bar| do
// handle & possibly rethrow if it's fatal
onexception |evt.ex| do
// either an unexpected exception has been
// thrown or the user has canceled our
// operation. Perform any cleanup
// necessary, and be sure to rethrow..
ReThrow();
end; // for loop
end; // workFunc
progress := DoProgress('vGauge, myOpts, workFunc);
if progress = 'cancelled then
// this is another place to clean up after being
// cancelled
The workFunc function’s argument, theContextView , is the status slip that
contains the gauge. A reference to this view is passed to your work function so that
you can send it
SetStatus messages. Note that workFunc is structured in a way
that permits it to call the progress slip’s SetStatus method at regular intervals,
passing values used to update the progress slip’s gauge and message string.