Special-Purpose Objects for Data Storage and Retrieval

Using Special-Purpose Data Storage Objects

Getting the Store Part

12

Store parts (also known as package stores) are made available by the

GetPackageStore

function. Package stores do not appear in the

GetStores

result array, which is reserved for normal store objects.

The

GetPackageStore

function retrieves the store by name, so each package

store must be given a unique name when it is built. Generally, this is ensured by
including the unique package symbol in the store name.

Accessing Data in Store Parts

12

Although store parts support most of the messages that normal soups do, remember
that store parts are read-only. Sending to a store part those messages that would
normally change a soup or its store (such as

CreateSoupXmit

,

SetName

and so

on) throws an exception.

Another thing to keep in mind is that soups on store parts do not participate in
union soups. You need to check explicitly for the presence of your store and soup.

The

GetPackageStore

and

GetPackageStores

functions provide two

different ways to find a store part. Usually, you use the global function

GetPackageStore

and pass the name of the store part you created as its

argument. Assuming the example code shown in "Creating a Store Part" on
page 12-13 was used to create the store part, you could use code similar to the
following example to check for the existence of the read-only soup residing on the
store part:

local pStore := GetPackageStore(kStoreName) ;
if pStore then

local pSoup := pStore:GetSoup(kSoupName) ;

Using Mock Entries

12

A mock entry has two parts: one is a cached frame, which the NewtonScript
interpreter treats as the entry when doing assignment, slot lookup, and so on; the
other is the handler frame that retrieves the actual entry data and implements a
suite of methods that manipulate it.

Topics discussed in this section include

implementing the

EntryAccess

method

creating a mock entry

testing the validity of a mock entry

getting entry cache data

getting and setting mock entry handlers

implementing additional handler methods