Apple Newton Programmer’s Newton 2.0 (for Newton 2.0) - Manual (Page 758)

C H A P T E R 2 1
Routing Interface
21-10 Using Routing
Getting and Verifying the Target Object 21
When the user first taps the Action button, but before a choice is made from the
picker, the Routing interface sends the Action button view the
GetTargetInfo
message, passing the symbol 'routing as a parameter. The purpose of this
message is to get the target object to be routed and the target view in which it
resides. Usually, these items are stored in slots named
target and targetView
in your application. If you set up and use such slots in your views, you don’t need
to implement the
GetTargetInfo method because this is a root view method
that is found by inheritance. The root view method simply looks for the slots
target and targetView , starting from the receiver of the message, which is the
Action button view. It returns these slots in a frame called the target information
frame. If you don’t use these slots in your views, you’ll need to implement the
GetTargetInfo method to return them.
You’ll need to implement the GetTargetInfo method if the user has selected
multiple items to route. In this case, you’ll need to construct a single object that
encapsulates the multiple items selected for routing, because the target must be a
single object and it can’t be a standard cursor. In your
GetTargetInfo method
you can use the function CreateTargetCursor to create a multiple-item target
object from the selected items.
Note
In most cases the target object is a frame. In some cases you
might want to route a nonframe object such as a string or binary.
The Routing interface supports nonframe target objects; however,
other system services such as Filing may require target objects
that are frames, so you may not be able to use the same target
with them. Note also that nonframe target objects must have a
meaningful class for use with the Routing interface.
◆
Once the user chooses a transport-based routing action from the Action picker, the
system creates a new item frame containing some default slots and values for the
target item. This is done by means of the transport method
NewItem . One slot that
is initialized by NewItem is the appSymbol slot of the item frame. The value for
this slot is obtained from the appSymbol slot of the application doing the routing
(through inheritance from the Action button view).
Then, just before the routing slip is opened, the Routing interface sends the
message
VerifyRoutingInfo to the view identified by the appSymbol slot in
the item frame. This is normally your application base view. However, if you are
doing routing from a view created by
BuildContext , for example, the
appSymbol slot might be missing because such views don’t automatically include
this slot. You must include an appSymbol slot in such a view, if you need to use
the VerifyRoutingInfo message, since the appSymbol slot determines where
this message is sent.