[TYPO3-mvc] How to send object form data in a link URL

[g4-lisz at tonarchiv.ch]

Hi

I wrote a search form to search for domain objects by certain properties 
(e.g. clients by cities).

For this reason i made the class "SearchDemand". It contains all the 
properties, against which objects will be matched:

class Tx_Myext_Domain_Model_SearchDemand extends 
Tx_Extbase_DomainObject_AbstractEntity {
     /**
      * @var Tx_Myext_Domain_Model_City The demanded City
      **/
     protected $city;

[etc.]
}

The controller action for the search form looks like this:

function searchformAction(Tx_Myext_Domain_Model_SearchDemand $demand=NULL) {
     $this->view->assign('demand', $demand);
     $this->view->assign('cities', $this->citiyRepository->findAll());
}

function resultAction(Tx_Myext_Domain_Model_SearchDemand $demand) {
     $this->view->assign('clients', 
$this->clientRepository->findByDemand($demand));
}

The repository's finder method looks like this:

function findByDemand(Tx_Myext_Domain_Model_SearchDemand $demand)
     $query = $this->createQuery();
     $constraints = array();

     if ( ($city = $demand->getCity()) != NULL) {
         $constraints[] = $query->equals('person.city', $city);
     }
[etc.]
}

This works as expected as long i use the form viewhelper with select in 
my views.

But i'd like to have a list of all cities on my search page, not a 
select form. Ever city name should just be a link.

I tried something like this in the search form view:

<f:for each="cities" as="city"><a 
href="{f:uri.action(action:'result',arguments:{demand:{city:city}})}">{city.name}</a></f:for>

This gave me an error: "Request hash (HMAC) checking failed. The 
parameter __hmac was invalid or not set, and objects were modified."

I also tried this in my view:

<f:form action="results" object="{demand}" id="search_form">
<input type="hidden" id="input_city" 
name="tx_myext_myplugin[demand][city]" value="">
<f:for each="{cities}" as="city"><a href="#" 
onClick="$('#input_city').val('{city.uid}');$('#search_form').submit();">{city.name}</a></f:for>
</f:form>

No success neither.

What magic do i need to get this working?

Many thanks in advance...!
Cheers, T.