Apple WebObjects 3.5 Uživatelský manuál stáhnout pdf (Strana 100)

Chapter 6 Creating Reusable Components

100

The parentAction attribute identiﬁes a callback method, one that the child

component invokes in the parent when the user clicks the Yes or No link. The

exitStatus attribute identiﬁes a variable that the parent can check to discover which

of the two links was clicked. This attribute passes state information from the

child to the parent. A reusable component can have any number of callback and

state attributes, and they can have any name you choose.

Now let’s look at the revised child component. The template ﬁle for the

AlertPanel component has to declare the positions of the added Yes and No

hyperlinks. (Only excerpts of the implementation ﬁles are shown here.)

Child's Template File (excerpt)

<TD>

</TD>

<TD>

</TD>

The corresponding declarations ﬁle binds these declarations to scripted

methods:

Child's Declarations File (excerpt)

NOCHOICE: WOHyperlink {

action = rejectChoice;

string = "No";

};

YESCHOICE: WOHyperlink {

action = acceptChoice;

string = "Yes";

};

And the script ﬁle contains the implementations of the rejectChoice and acceptChoice

methods:

Child's Script File (excerpt)

id exitStatus;

id parentAction;

- rejectChoice {

exitStatus = NO;

return [self performParentAction:parentAction];

}

- acceptChoice {

exitStatus = YES;

return [self performParentAction:parentAction];

}

Note that exitStatus and parentAction are simply component variables. Depending on

the method invoked,

exitStatus can have the values YES or NO. The parentAction

variable stores the name of the method in the parent component that will be

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