Apple Newton Utilities Uživatelská příručka stáhnout pdf (Strana 520)

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CHAPTER 12

Special-Purpose Objects for Data Storage and Retrieval

12-14 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

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