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PONull in Flex ComboBox
 

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    <p>How can you make a ComboBox where the user can select <code>null</code>?</p> <p>If you simply create a combobox with <code>null</code> in the dataprovider, the value appears but the user cannot select it:</p> <pre><code>&lt;mx:ComboBox id="cb" dataProvider="{[null, 'foo', 'bar']}" /&gt; </code></pre> <p>Is there a way to make that null selectable?</p> <p>A workaround is to add an item into the dataProvider that is not null but 'represents' null; and then map between null and that object every time you access the combobox. But that's not really an elegant solution; you would always have to keep this mapping in mind in all code that accesses a 'nullable' combobox...</p> <p>Edit: expanding on why I don't like the workaround: It could be done in a subclass of course, but either I introduce new attributes (like <code>nullableSelectedItem</code>); but then you have to be careful to always use these attributes. Or I override ComboBoxes <code>selectedItem</code>; but I'm affraid that is going to break the base class: it might not like something changing its idea of what the current selected item is from within. And even this fragile hack works, on top of <code>selectedItem</code> and <code>dataProvider</code> this nullItem then also needs to be handled special in <code>data</code> and <code>listData</code> for renderers, in <code>labelFunction</code>, and then it's probably still being exposed in events the ComboBox sends... It might work, but it's quite a hack just to fix the problem that if the user clicks on the item it isn't activated (for the rest the ComboBox handles null fine). (Another alternative is to have a ui component delegate to a ComboBox, but that's even much more code just to avoid this small problem)</p>
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    1. COYou could make a subclass of ComboBox which encapsulates just this nulling behavior.
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