src/Provider/Indexable.php
private function buildExpressionCallback($type, $object, $callback)
    {
        $expression = $this->getExpressionLanguage();
        if (!$expression) {
            throw new \RuntimeException('Unable to process an expression without the ExpressionLanguage component.');
        }

        try {
            $callback = new Expression($callback);
            $expression->compile($callback, [
                'object', $this->getExpressionVar($object),
            ]);

            return $callback;
        } catch (SyntaxError $e) {
            throw new \InvalidArgumentException(sprintf(
                'Callback for type "%s" is an invalid expression',
                $type
            ), $e->getCode(), $e);
        }
    }
private function buildExpressionCallback($type, $object, $callback)
    {
        $expression = $this->getExpressionLanguage();
        if (!$expression) {
            throw new \RuntimeException('Unable to process an expression without the ExpressionLanguage component.');
        }

        try {
            $callback = new Expression($callback);
            $expression->compile($callback, [
                'object', $this->getExpressionVar($object),
            ]);

            return $callback;
        } catch (SyntaxError $e) {
            throw new \InvalidArgumentException(sprintf(
                'Callback for type "%s" is an invalid expression',
                $type
            ), $e->getCode(), $e);
        }
    }
Processes a string expression into an Expression.

@param string $type
@param mixed  $object
@param string $callback

@return Expression