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CHAPTER 11

Data Storage and Retrieval

11-26 Using Newton Data Storage Objects

This section presumes understanding of the material in “About Data Storage on

Newton Devices” beginning on page 11-1.

Most applications store data as frames that reside in soup entries. You can create a

frame by simply deﬁning it and saving it in a variable, a constant, or a slot in

another frame. For example, the following code fragment deﬁnes a frame

containing the

aSlot and otherSlot slots. The frame itself is stored in the

myFrame variable. For all practical purposes you can treat variables that hold

NewtonScript objects as the objects themselves; hence, the following discussion

refers to the frame saved in the

myFrame variable as the myFrame frame.

myFrame := {aSlot: "some string data", otherSlot: 9258};

The myFrame frame contains two slots: the aSlot slot stores the "some

string data" string and the otherSlot slot stores the 9258 integer value.

Because every NewtonScript object encapsulates its own class data, you need not

declare types for NewtonScript data structures, including slots.

Frames are not persistent unless stored as soup entries. To add the

myFrame frame

to a soup, you must send a message to the appropriate soup object. You can obtain

a soup or union soup object by creating a new one or by retrieving a reference to

one that is already present.

To create a new union soup, use the

RegUnionSoup function to register its soup

deﬁnition with the system. The system uses this deﬁnition to create the union’s

member soups as needed to store soup entries.

The following code fragment saves the union soup object

RegUnionSoup returns

in the

myUSoup local variable. You might place code like this example in your

application (

form) part’s InstallScript function or your application base

view’s

ViewSetupFormScript method:

local aSlotIndexSpec := {structure: 'slot, path: 'aSlot,

type: 'string};

local otherSlotIndexSpec := {structure: 'slot, path: 'otherSlot,

type: 'int};

local mySoupDef := {name: "mySoup:mySig",

userName: "My Soup",

ownerApp: '|MyApp:MySig|,

ownerAppName : "My Application",

userDescr: "This is the My Application soup.",

indexes: [aSlotIndexSpec,otherSlotIndexSpec]

};

local myUsoup := RegUnionSoup('|MyApp:MySig|,mySoupDef);

Note the use of the mySig developer signature as a sufﬁx to ensure the uniqueness

of the values of the

name and ownerApp slots. For more information regarding

developer signatures, see Chapter 2, “Getting Started.”

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