Apple Newton Utilities Guia do Utilizador descarregar pdf (Página 490)

100

101

CHAPTER 11

Data Storage and Retrieval

11-58 Using Newton Data Storage Objects

Saving Frames as Soup Entries 11

To save a frame as a soup entry, pass the frame to either of the union soup methods

AddToDefaultStoreXmit or AddToStoreXmit, or pass it to the AddXmit

soup method. Each of these methods transforms the frame presented as its

argument into a soup entry, returns the entry, and transmits a change notiﬁcation

message. The following code example illustrates the use of the

AddToDefaultStoreXmit method:

local myFrame := {text: "Some info", color: 'blue};

// assume mySoupDef is a valid soup definition

local myUSoup := RegUnionSoup(mySoupDef)

myUSoup:AddToDefaultStoreXmit(myFrame,'|MyApp:MySig|);

The new soup entry that these methods create consists of the frame presented to the

entry-creation method, along with copies of any data structures the frame

references, as well as copies of any data structures those structures reference, and

so on. Thus, you must be very cautious about making soup entries out of frames

that include references to other data structures. In general, this practice is to be

avoided—it can result in the creation of extremely large entries or entries missing

slots that were present in the original frame.

For example, the presence of a

_parent slot in the frame presented as an

argument to these methods causes the whole

_parent frame (and its parent, and

so on) to be stored in the resulting entry, potentially making it extremely large. An

alternative approach is to store a key symbol in the data and ﬁnd the parent object

in a frame of templates at run time.

Do not include

_proto slots in frames presented to methods that create soup

entries. These slots are not written to the soup entry and are missing when the entry

is read from the soup.

Do not save magic pointers in soup entries. Because the objects they reference are

always available in ROM, saving magic pointers is unnecessary and may cause the

entries to exceed the maximum permissible size.

Circular pointers within an entry are supported, and an entry can refer to another

by using an entry alias.

The size of an individual entry is not limited by the NewtonScript language; however,

due to various practical limitations, entries larger than about 16 KB can impact

application performance signiﬁcantly. For best performance, it is recommended

that you limit the size of individual entries to 8 KB or less. Note that this total does

not include data held by virtual binary objects that the entry references; virtual

binary objects save their data separately on a store speciﬁed when the virtual binary

object is created. For more information, see “Virtual Binary Objects” on page 12-2

in Chapter 12, “Special-Purpose Objects for Data Storage and Retrieval.”

1 2 ... 485 486 487 488 489 490 491 492 493 494 495 ... 941 942

Comentários a estes Manuais

Sem comentários

Apple Newton Utilities Guia do Utilizador Página 490

Comentários a estes Manuais

Manuais e produtos relacionados com Software Apple Newton Utilities