Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 804)

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CHAPTER 22

Transport Interface

22-16 Using the Transport Interface

if dataDef then

begin

item.fromRef := dataDef:MakeNameRef(persona,

addressingClass);

// add other slots or extract routing info here

end;

item;

end;

During a receive operation, the transport itself must invoke the NewFromItem

method to get a new In/Out Box item frame. This method copies most slots from

the received item to the new In/Out Box item frame. Additionally, it inserts the

destAppSymbol slot value (if included) in the received frame into the appSymbol

slot in the new frame.

Finally, the transport should call

ItemCompleted to register the item in the In

Box (see the following section).

Completion and Logging 22

After your transport ﬁnishes processing an item (either sending or receiving, with

or without errors), you must send the transport the message

ItemCompleted.

This method must be used when an item is altered in any way. It performs several

operations, including setting the state and error status of the item; sending the

ItemCompletionScript callback message to the application; handling error

conditions; and saving, logging, or deleting the item, depending on the logging

preferences.

Send the

ItemCompleted message only after your transport has completely

processed an item. If you send this message before you know that the item was

delivered successfully, for example, there’s a possibility that the item will be lost.

ItemCompleted was called as the result of an error, it calls HandleError to

translate the error code and notify the user. If you want to perform your own error

notiﬁcation, you can override the

HandleError method.

Note that the

ItemCompleted method in protoTransport sends the

ItemCompletionScript callback message to the application only if the item

contains a

completionScript slot that is set to true. You must set this slot

if you want the callback message to be sent. For more information on

ItemCompletionScript see Newton Programmer’s Reference (page 18-33).

To perform logging,

ItemCompleted sends your transport the message

MakeLogEntry, passing a log entry to which you can add slots. The

protoTransport object includes a default MakeLogEntry method, but you

should override this method to add transport-speciﬁc slots to the log entry.

The default method simply adds a

title slot to the log entry. The

GetItemTitle transport method is called to get the title.

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