Apple Newton Utilities User's Guide download pdf (Page 489)

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CHAPTER 11

Data Storage and Retrieval

Using Newton Data Storage Objects 11-57

Note that if the query used to generate the cursor speciﬁes a beginKey value, the

CountEntries method starts counting at the first valid entry having an index key

value equal to or greater than the

beginKey value. Similarly, if the query that

generated the cursor used an

endKey value, the CountEntries method stops

counting at the last valid entry having an index key value equal to or less than the

endKey value.

Note that the use of the

CountEntries method is somewhat time-consuming and

may increase your application’s heap space requirements; for performance reasons,

use this method only when necessary.

Getting the Current Entry’s Index Key 11

The EntryKey cursor method returns the index key data associated with the

current cursor entry without reading the entry into the NewtonScript heap. Note,

however, that under certain circumstances the value returned by this method does

not match the entry’s index key data exactly. For more information, see “Limitations

of Index Keys” on page 11-52.

Copying Cursors 11

You can clone a cursor to use for browsing soup entries without disturbing the

original cursor. Do not use the global functions

Clone or DeepClone to clone

cursors. Instead, use the

Clone method of the cursor to be copied, as shown in the

following code fragment:

local namesUSoup:= GetUnionSoupAlways(ROM_CardFileSoupName);

local namesCursor := namesUSoup:Query(nil);

local cursorCopy:= namesCursor:Clone();

Using Entries 11

This section discusses the functions and methods that work with soup entry objects

returned by cursors. This section describes

■ adding entries to soups

■ removing entries from soups

■ saving references to entries

■ modifying entries

■ replacing entries

■ sharing entry data

■ copying entry data

■ using the entry cache effectively

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