how to: specify multiple selected items in a multi-select element using typo3 fluid?

Question

In fluid code like this, how do I specify which items are preselected?

<f:form.select name="coupon" options="{couponoptions}" multiple="true" size="10"/>   

the couponoptions is an array with uid values and name label pairs defined like so:

    $coupons = $this->couponRepository->findAll();

    foreach($coupons as $coupon) {
        $couponoptions[$coupon->getUid()] = $coupon->getName();

    }

The options all show up but I don't know how to specify which are preselected.

I am using typo3 v4.5.32 with fluid 1.3.

Thanks.

PS, the preselected items are found in php like so:

    $old = $this->couponsAttachedRepository->findAll();
    foreach($old as $o) {
        $c = $o->getCoupon();
        $couponsselected[$c->getUid()] = $c->getUid();
    }

PPS: I would be happy to not use the f:form.select tag if I could get pass the options ina as a string like so {optionsstring} but when I try that the markup gets changed to html entities eg my < becomes '& lt;' etc. Is there way around that?

ANSWER from lorenz: ( I was so close, I just had to add the value like so)

 <f:form.select name="coupon" options="{couponoptions}" value="{couponsselected}" multiple="true" size="10"/>   

Answer 1

You can use the value property to do a preselection, where the array key is the value:

PHP:

$couponOptions = array('a' => 'Value A', 'b' => 'Value B');

Fluid:

<f:form.select name="coupon" options="{couponOptions}" multiple="true" value="a" size="10"/>