Apple Newton Utilities Guia do Utilizador descarregar pdf (Página 459)

100

101

CHAPTER 11

Data Storage and Retrieval

Using Newton Data Storage Objects 11-27

When creating soups from within your application (form) part’s InstallScript

function, remember that this function calls the

EnsureInternal function on

all values it uses. Thus, instead of passing references such as

partFrame.theForm.myMainSoupDef to the RegUnionSoup function, paste

a local copy of your soup deﬁnition into your application part’s

InstallScript

function for its use.

The

RegUnionSoup function uses the value of your soup deﬁnition’s name slot to

determine whether a particular soup deﬁnition has already been registered. You

need not be concerned with registering a soup deﬁnition twice as long as you don’t

registers a soup deﬁnition when it opens can always use the union soup object

returned by the

RegUnionSoup function—if the union soup named by the soup

deﬁnition exists, this function returns it; otherwise, this function uses the speciﬁed

soup deﬁnition to create and return a new union soup.

The next code fragment uses the

AddToDefaultStoreXmit function to add the

myFrame frame to the myUSoup union soup. This function creates a new member

soup to hold the entry if necessary. The soup is created on the store indicated by the

user preference specifying where new items are kept.

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

At this point, we have created a soup on the store speciﬁed by the user and added

an entry to that soup without ever manipulating the store directly.

Because you’ll often need to notify other applications—or even your own

application—when you make changes to soups, all the methods that modify

soups or soup entries are capable of broadcasting an appropriate soup change

notiﬁcation message automatically. In the preceding example, the

AddToDefaultStoreXmit method notifies applications registered for changes

to the

myUSoup union soup that the '|MyApp:MySig| application added an

entry to this union soup. For more information, see “Callback Functions for Soup

Change Notiﬁcation” (page 9-14) in Newton Programmer’s Reference.

Most of the time, your application needs to work with existing soups rather than

create new ones. You can use the

GetUnionSoupAlways function to retrieve an

existing soup by name.

Once you have a valid soup object, you can send the

Query message to it to

retrieve soup entries. The

Query method accepts a query speciﬁcation frame as its

argument. This frame deﬁnes the criteria soup entries must meet in order to be

retrieved by this query. Although you can pass

nil as the query spec in order to

retrieve all the entries in a soup, usually you’ll want to retrieve some useful subset

of all entries. For example, the following code fragment retrieves from

myUsoup

all entries having an

aSlot slot. For an overview of the use of query speciﬁcations,

see “Using Queries” beginning on page 11-38.

1 2 ... 454 455 456 457 458 459 460 461 462 463 464 ... 941 942

Comentários a estes Manuais

Sem comentários

Apple Newton Utilities Guia do Utilizador Página 459

Comentários a estes Manuais

Manuais e produtos relacionados com Software Apple Newton Utilities