Apple Newton Utilities Uživatelská příručka stáhnout pdf (Strana 796)

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CHAPTER 22

Transport Interface

22-8 Using the Transport Interface

the routing slip is not closed. If TransportChanged returns nil, then the

transport is changed and operations continue normally.

You can use the function

GetGroupTransport to determine the name of the

current (last-used for sending by the user) transport in a group. Note that when you

install a grouped transport, it becomes the current transport for that group.

Transports that are part of a group are individually selectable on the Send, Receive,

and Preferences pickers in the In/Out Box.

Sending Data 22

The Out Box sends the SendRequest message to your transport when data needs

to be sent. If your transport supports sending data, you must deﬁne this method to

actually send the data. For a complete description of the

SendRequest method,

see “SendRequest” (page 19-33) in Newton Programmer’s Reference.

The Out Box puts its own query information in the

request frame argument to

SendRequest. Your SendRequest method must pass this frame to the

ItemRequest message to get the item (or next item) to send. In your

SendRequest method, keep calling ItemRequest until it returns nil,

signalling no more items to send. For a complete description of the

ItemRequest

method, see “ItemRequest” (page 19-26) in Newton Programmer’s Reference.

If the

body slot of an item originally contained an alias, the alias is automatically

resolved by

ItemRequest. That is, items returned by ItemRequest always

contain a

body slot that is not an alias.

Note that you can save entry aliases to items returned by

ItemRequest, if you

want. Later, when using them, make sure that

ResolveEntryAlias returns a

non-

nil value, and that the item state slot is set as expected.

You can choose to comply with or ignore any request to send, depending on the

communication resources available and their status. If you choose to comply, your

SendRequest method must obtain one or more items from the Out Box by using

the

ItemRequest method, and send them by whatever means the transport uses

to communicate. For example, most transports use the Endpoint interface to

establish and operate a connection.

request.cause is 'submit, the item is queued in the Out Box for later sending,

but the Out Box still notiﬁes the transport by sending it this

SendRequest

message so that the transport knows there are items waiting to be sent. Typically, a

transport doesn’t need to take any immediate action on items where

request.cause

'submit, so you can use code like this to simply return:

If request.cause = 'submit then return nil;

The item.connect slot contains a Boolean value indicating if the user chose to

send the item now (

true) or later (nil).

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