Apple Newton Utilities Guide de l'utilisateur télécharger pdf (Page 492)

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CHAPTER 11

Data Storage and Retrieval

11-60 Using Newton Data Storage Objects

When the frame is constructed from the entry, it is cached in memory. At this point,

you can add, modify, and delete slots just as you would in any other frame;

however, the changes do not persist until the

EntryChangeXmit function is

called for that particular entry. The

EntryChangeXmit function writes the cached

entry frame back to the soup, replacing the original entry with the changed one.

If the

EntryUndoChangesXmit function is called, the changes are thrown out

and the entry is restored to its original state. This function disposes of the cached

entry frame and restores the reference to the original uncached entry, just as if the

original entry was never referenced. Note that you can use the

FrameDirty

function to determine whether a cached entry has been modiﬁed since it was read

into the NewtonScript heap; however, this function does not detect changes to

individual characters in a string (a common operation for

clParagraphView

views). For more information, see “FrameDirty” (page 9-69) in Newton

Programmer’s Reference.

The following code example gets an entry from the

namesUSoup union soup,

changes it, and writes the changed entry back to the soup:

local namesUSoup := GetUnionSoupAlways(ROM_CardFileSoupName);

local namesCursor := namesUSoup:Query(nil);

local theEntry := namesCursor:Entry();

if theEntry then

begin

theEntry.cardType := 4;

EntryChangeXmit(theEntry, '|MyApp:MySig|);

end;

It’s not always easy to determine the best time to write a cached entry back to its

soup. For example, it would be inappropriate to call a function like

EntryChangeXmit from the ViewChangedScript method of a

protoLabelInputLine view. When the user enters data on the input line with

the keyboard, the

ViewChangedScript is called after every key press. Calling

the

EntryChangeXmit function for every key press would be noticeably slow.

In some situations, the appropriate time to call

EntryChangeXmit is more

obvious. For example, a natural time to call

EntryChangeXmit would be when

the user dismisses an input slip.

Moving Entries 11

You can use the MoveTarget method of the root view to move (not copy) an

entry into the same-named soup on another store. For example, you would use

this method to move entries from one union soup member to another. For more

information, see “System-Supplied Filing Methods” (page 12-11) in Newton

Programmer’s Reference.

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Apple Newton Utilities Guide de l'utilisateur Page 492

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