Apple Newton Utilities Uživatelská příručka stáhnout pdf (Strana 513)

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CHAPTER 12

Special-Purpose Objects for Data Storage and Retrieval

Using Special-Purpose Data Storage Objects 12-7

Using Special-Purpose Data Storage Objects 12

This section describes how to use entry aliases, virtual binary objects (VBOs),

store parts, and mock entries. This section presumes understanding of the

conceptual material presented in preceding sections.

Using Entry Aliases 12

This section describes how to create entry aliases, how to save them, and how to

resolve them.

Aliases can be created for any entry that resides in a soup or union soup. Aliases

cannot be created for mock entry objects.

You must not assume that an entry alias is valid. When the entry to which it refers

is deleted or is moved to another store, an entry alias becomes invalid. Renaming a

store renders invalid all aliases to entries residing on that store.

The

MakeEntryAlias function returns an alias to a soup entry, as shown in the

following code fragment:

// return entries that contain "bob" and "Apple"

local myCurs:= namesSoup:Query({ entireWords: true,

words:["Bob", "Apple"]});

// keep an alias to bob around

local bobAlias := MakeEntryAlias(myCurs:Entry());

// but get rid of the cursor

myCurs := nil;

To save an entry alias, simply save it in a soup entry.

You can use the

ResolveEntryAlias function to obtain the entry to which the

alias refers, as shown in the following code fragment:

// continued from previous example

local bobEntry := ResolveEntryAlias(bobAlias);

Note that the ResolveEntryAlias function returns nil if the original store,

soup, or entry to which the alias refers is unavailable.

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