Apple Newton Utilities Podręcznik Użytkownika Pobierz pdf (Strona 773)

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CHAPTER 21

Routing Interface

Using Routing 21-25

cursors, refer to Chapter 11, “Data Storage and Retrieval.” Note that only these

three cursor methods are supported for use with cursors returned by

GetTargetCursor.

Note that

GetTargetCursor works with any kind of target data, whether or not

it’s a cursor. So you don’t need to call

TargetIsCursor to check before calling

GetTargetCursor.

Here’s an example of a

RouteScript method that uses GetTargetCursor to

operate on multiple items:

MyActionFunc := func(target,targetView)

begin

local curs := GetTargetCursor(target,nil);

local e := curs:Entry();

while e do begin

:DoMyAction(e); // do the operation

e := curs:Next();

end;

// update display here

end;

Handling No Target Item 21

If the target item returned by GetTargetInfo is nil, this indicates that no target

item is selected or there is nothing to do when the Action button is pressed. In this

case, the system displays a warning message to inform the user of that fact. To take

advantage of this warning message feature, all application-speciﬁc routing actions

must be disabled when there is no target. (You may want to include some actions

even when there is no target; in this case, you can ignore this section.)

To disable application-speciﬁc routing actions when there is no target, you can do

one of two things:

■ Deﬁne a GetTitle method in the routeScripts frame for each action,

instead of a

title slot. Then return nil from the GetTitle method to

prevent that action from showing up on the picker.

■ Deﬁne a GetRouteScripts method in your application, instead of a

routeScripts slot. Then return nil or an empty array from the

GetRouteScripts method to prevent any actions from showing up on

the picker.

Note that there are different messages displayed when there is no target item (the

target is

nil) and when there are no actions available for the target item.

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