Apple WebObjects 3.5 Tools And Techniques Bedienungsanleitung PDF herunterladen (Seite 80)

Chapter 3 Working With Dynamic Elements

the WOConditional’s contents are displayed. If condition is false (0), the contents

aren’t displayed.

condition can be bound to a variable or to method that returns a Boolean value.

(WebScript and Objective-C use the constants

YES and NO; Java uses true and false.)

To bind

condition (or any other attribute that takes a Boolean) to a constant value,

enter

YES or NO in the bindings Inspector.

To create a conditional, click in the toolbar.

Note: Any selected elements will be contained within the conditional.

To bind to a conditional, click a variable or method and drag to one of the

conditional’s outer icons. The Inspector appears, displaying the bindings for the

WOConditional, with the

condition attribute selected by default. Complete the

binding by clicking Connect Variable, or choose a different attribute to bind.

There is a shortcut for binding the condition attribute. Drag from a key in the

object browser to the binding box in the conditional.

Sometimes, you want the equivalent of an “if-then-else” structure; that is, “if

the condition is true, display this text; if not, display this other text.” To

accomplish this, you can use the

negate attribute. If negate is true, then the

contents of the conditional are displayed only if

condition is false. To create an if-

then-else structure, do the following:

1. Create two WOConditionals.

2. Bind the

condition attribute of both of them to the same variable or method.

3. Bind the

negate attribute of the second one to YES (true).

By default,

negate is false, so you do not explicitly need to bind the ﬁrst

conditional’s negate attribute.

As with repetitions, you can “wrap” a conditional around a table row (see

“Repetitions”). When you do this, the conditional symbol doesn’t appear but

the row appears with a blue background.

Drag from the object browser to this box to bind the condition attribute

without opening the Inspector. The binding appears inside the box.

Contents of the conditional display if

condition is true.

Drag from the object browser to here

to bind (opensthe Inspector).

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