Data Storage and Retrieval

Using Newton Data Storage Objects

:MakeKey(["12345678901234567890", 3,

"ABCDEFGHIJKLMNOPQRSTUVWXYZ"],
['name.first, 'cardType, 'name.last] )

returns the key value

["12345678901234567890", 3, "ABCDEFGHIJKLMNO"]

The next example illustrates the truncation of subkeys when the total key size is
greater than 80 bytes. In this example, the first string in the string array is so long
that it uses up the entire 80 bytes allocated for the key, with the result that the first
string is truncated and the remaining key values are

nil

. Evaluating the following

code fragment in the Inspector

:MakeKey(["12345678901234567890abcdefghijjlmnopqrstuvwxyz",

3, "ABCDEFGHIJKLMNOPQRSTUVWXYZ12345678901234567890"],
['name.first, 'cardType, 'name.last] )

returns the key value

["12345678901234567890abcdefghijjlmnopqr", NIL, NIL]

Missing elements in the string array are treated as

nil

values. For example, the

following code fragment is missing the second two elements of the string array:

:MakeKey(["12345678901234567890],

['name.first, 'cardType, 'name.last] )

Evaluating this code fragment in the Inspector returns the key value

["12345678901234567890", NIL, NIL]

On the other hand, missing index paths cause this method to throw an exception. If
one of the index paths in a multiple-slot index is missing from the array passed as
the value of the indexPath parameter, the

MakeKey

method throws a "soup index

does not exist"

evt.ex.fr.store -48013

exception.

Using Cursors

11

This section discusses the functions and methods used to work with cursor objects
returned by the

Query

method of soups or union soups. Individual entries in soups

and union soups are manipulated by the entry functions described in the section
"Using Entries," later in this chapter. This section describes

getting the cursor

testing validity of the cursor

getting the currently referenced soup entry from the cursor

moving the cursor