Apple Newton Utilities Betriebsanweisung PDF herunterladen (Seite 496)

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CHAPTER 11

Data Storage and Retrieval

11-64 Using Newton Data Storage Objects

■ control how and when notiﬁcations are sent

The ﬁrst part of this section describes how to register and unregister a callback

function for execution in response to changes in a particular soup. The next part

describes the various notiﬁcations that may be sent. The last part of this section

describes how applications send soup change notiﬁcations.

Registering Your Application for Change Notiﬁcation 11

The RegSoupChange global function registers a callback function for execution

in response to changes in a particular soup. Note that this callback function must

not call either of the

RegSoupChange or UnRegSoupChange functions.

If your application needs to respond to changes in more than one soup, you’ll need

to call the

RegSoupChange function once on each soup for which your

application requires change notiﬁcation. This approach is valid for any system-

supplied soup except that used by the built-in Preferences application. For

notiﬁcation of changes to user preferences, you must call the

RegUserConfigChange function.

You can call the

RegSoupChange function at any time that makes sense for your

application. For example, you might do so from within your base view’s

viewSetupDoneScript method; however, this is only a suggested guideline. In

order to conserve available memory, your application should minimize the amount

of time callback functions remain registered.

The following code example shows how to register your application for notiﬁcation

of changes to the soup used by the built-in Names application:

local myFn := func (soupName, appSym, changeType, changeData)

begin

if (changeType) then

begin

if (changeType <> 'whatThe) then

print (changeType && "in the" && soupName &&

"soup by the" && GetAppName(appSym) &&

"application.");

else

print ("Unspecified changes occurred in the" &&

soupName && "soup.");

end;

// register for changes to soup used by built-in "Names" app

RegSoupChange(ROM_CardFileSoupName, '|myFn1:MyApp:MySig|, myFn);

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