Apple WebObjects 3.5 Manual de usuario descargar pdf (Pagina 99)

Intercomponent Communication

For reusable components to be truly versatile, there must also be a

mechanism for the child component to interact with the parent, either by

setting the parent’s variables or invoking its methods, or both. This

mechanism must be ﬂexible enough that a given child component can be

reused by various parent components without having to be modiﬁed in any

way. WebObjects provides just such a mechanism, as illustrated by the

following example.

Consider an AlertPanel component like the one described above, but with

the added ability to accept user input and relay that input to a parent

component. The panel might look like the one in Figure 29.

Figure 29. An Alert Panel That Allows User Input

As in the earlier example, you use this component by simply declaring its

position within the HTML page:

Parent's Template File

<HTML>

<HEAD>

<TITLE>Alert</TITLE>

</HEAD>

<BODY>

</BODY>

</HTML>

The corresponding declarations ﬁle reveals two new attributes (indicated in

bold):

Parent's Declarations File (excerpt)

ALERT: AlertPanel {

infoString = message;

infoFontSize = 4;

infoFontColor = "#500000";

alertString = "New Release";

alertFontColor = "#A00000";

alertFontSize = 6;

tableWidth = "50%";

parentAction = "respondToAlert";

exitStatus = usersChoice ;

};

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Apple WebObjects 3.5 Manual de usuario Pagina 99