WebObjects Viewed Through Its Classes

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Page Level

At the page level, objects of many classes (most of them private) work together to compose the HTML content of response pages (see Figure 18). Many of the same objects also set their variable values from data entered into request pages and respond to user actions.

Figure 18. Request-Response Loop: Page Level

Two major branches of these objects descend from WOElement: WOComponent objects, which represent components, and WODynamicElement objects, which represent dynamic HTML elements on the page. For details on how this happens and for more on these classes, see "How HTML Pages Are Generated".

Four classes are involved at this level. Of these four, most developers only interact with WOComponent.

WOComponent
Represents an integral, reusable page (or portion of a page) for display in a web browser.
WOElement
Declares the three component action request-handling methods: takeValuesFromRequest:inContext:, invokeActionForRequest:inContext:, and appendToResponse:inContext:. WOElement is an abstract class. Each node in an object graph, which represents the HTML elements of a component and their relationships, is an object that inherits from WOElement.
WODynamicElement
An abstract class for subclasses that generate particular dynamic elements.
WOAssociation
Knows how to find and set a value by reference to a key. WODynamicElement objects generally have WOAssociation instance variables.

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