Apple WebObjects 3.5 Uživatelský manuál stáhnout pdf (Strana 45)

Action Methods

// Java example

public Component showPart() {

Error errorPage;

Inventory inventoryPage;

if (isValidPartNumber(partNumber)) {

errorPage = (Error)application().pageWithName("Error");

errorPage.setErrorMessage("Invalid part number " +

partnumber);

return errorPage;

}

inventoryPage = (Inventory)

application().pageWithName("Inventory");

inventoryPage.setPartNumber(partnumber);

return inventoryPage;

}

Action methods don’t have to return a new page. They can instead direct

the application to use the request page as the response page by returning

nil

(

null in Java). For example, in the Visitors application, the recordMe action

method in the Main page records the name of the last visitor, clears the text

ﬁeld, and redraws itself:

// WebScript Visitors Main.wos

- recordMe

{

if ([aName length]) {

[[self application] setLastVisitor:aName];

[self setAName:@""]; // clear the text field

}

// Java Visitors Main.java

public Component recordMe

{

if (aName.length != 0) {

((Application)application()).setLastVisitor(aName);

aName = ""; // clear the text field

}

return null;

}

Note: Always return nil (null) in an action method instead of returning self (this).

Returning

nil uses the request component as the response component.

Returning

self uses the current component as the response component. At

ﬁrst glance, these two return values seem to do the same thing. However, if

the action method is in a component that’s nested inside of the request

component, a return value of

self will make the application try to use the

nested component, which represents only a portion of the page, as the

response component. This, most likely, is not what you want. Therefore, it

is safer to always return

nil.

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