Apple Newton Utilities Betriebsanweisung PDF herunterladen (Seite 521)

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CHAPTER 12

Special-Purpose Objects for Data Storage and Retrieval

Using Special-Purpose Data Storage Objects 12-15

Implementing the EntryAccess Method 12

Each of your mock entry handler frames must supply an EntryAccess method

that creates a cached frame containing the mock entry’s data, installs the cached

frame in the mock entry, and returns the cached frame. This method is called when

the system attempts to access a cached frame that is not present.

The system passes the mock entry to your

EntryAccess method when it is

invoked. This method calls the

EntrySetCachedObject function to install the

cached frame in the mock entry and then returns the cached frame.

The following code fragment provides a simple example of an

EntryAccess method:

myHandler := {

object: {foo: 'bar},

EntryAccess: func (mockEntry)

begin

// install cached frame

EntrySetCachedObject(mockEntry, object);

// return cached frame

object;

end,

// your additional slots and methods here

…}

Creating a New Mock Entry 12

The NewMockEntry global function creates a new mock entry object having a

speciﬁed handler and cached frame. Your application can use this method to create

a new mock entry; for example, in response to a

mockSoup:Add() message.

The handler frame you pass to the

NewMockEntry function must deﬁne an

EntryAccess method, as described in “Implementing the EntryAccess Method”

on page 12-15. The handler may also contain supporting methods or data used by

the mock entry; for example, it might hold information local to a speciﬁc mock

entry or information required to retrieve the mock entry’s data.

Depending on your needs, you can create new mock entries with or without their

corresponding cached frames. To create a mock entry with its cached frame already

installed, pass both the handler and the cached frame to this function.

To create a mock entry without a cached frame, pass

nil as the value of the

cachedObject parameter to the NewMockEntry function. When a slot in the

returned mock entry is accessed, the handler’s

EntryAccess method is invoked

to create the cached entry if it is not present.

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