Custom FlowQuery Operations

The FlowQuery EelHelper provides you with methods to traverse the ContentRepository. Implementing custom operations allows the creation of filters, sorting algorithms and much more.

#Create FlowQuery Operation

Implementing a custom operation is done by extending the Neos\Eel\FlowQuery\Operations\AbstractOperation class. The Operation is implemented in the evaluate method of that class.

To identify the operation late on in Fusion the static class variable $shortName has to be set.

If you pass arguments to the FlowQuery Operation they end up in the numerical array $arguments that is handed over to the evaluate method.

namespace Vendor\Site\FlowQuery\Operation;

use Neos\Eel\FlowQuery\FlowQuery;
use Neos\Eel\FlowQuery\Operations\AbstractOperation;

class RandomElementOperation extends AbstractOperation {

        /**
         * {@inheritdoc}
         *
         * @var string
         */
        static protected $shortName = 'randomElement';

        /**
         * {@inheritdoc}
         *
         * @param FlowQuery $flowQuery the FlowQuery object
         * @param array $arguments the arguments for this operation
         * @return void
         */
        public function evaluate(FlowQuery $flowQuery, array $arguments) {
                $context = $flowQuery->getContext();
                $randomKey = array_rand($context);
                $result = array($context[$randomKey]);
                $flowQuery->setContext($result);
        }
}

In Fusion you can use this operation to find a random element of the main ContentCollection of the Site-Node:

randomStartpageContent = ${q(site).children('main').children().randomElement()}

Note

To override an existing operation define another operation with the same shortName and a higher priority.

#Create Final FlowQuery Operations

If a FlowQuery operation does return a value instead of modifying the FlowQuery Context it has to be declared $final.

namespace Vendor\Site\FlowQuery\Operation;

use Neos\Eel\FlowQuery\FlowQuery;
use Neos\Eel\FlowQuery\Operations\AbstractOperation;

class DebugOperation extends AbstractOperation {

        /**
         * If TRUE, the operation is final, i.e. directly executed.
         *
         * @var boolean
         * @api
         */
        static protected $final = TRUE;

        /**
         * {@inheritdoc}
         *
         * @param FlowQuery $flowQuery the FlowQuery object
         * @param array $arguments the arguments for this operation
         * @return void
         */
        public function evaluate(FlowQuery $flowQuery, array $arguments) {
                return \Neos\Flow\var_dump($flowQuery->getContext(), NULL, TRUE);
        }
}

#Further Tips

For checking that the operation can actually work on the current context a canEvaluate method can be implemented.
In your FlowQuery evaluate function you can apply a filter function by pushing a filter operation. So if you want to filter for all nodes which have a email property set use: $flowQuery->pushOperation('filter', [ '[email != ""' ]);