Apple Newton Utilities User's Guide download pdf (Page 485)

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CHAPTER 11

Data Storage and Retrieval

Using Newton Data Storage Objects 11-53

mySoup: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

mySoup: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:

mySoup: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

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