src/Configuration/Option/Aggregate.php
protected function getConnectionInitializer(OptionsInterface $options, $callable)
    {
        if (!is_callable($callable)) {
            $class = get_called_class();

            throw new \InvalidArgumentException("$class expects a valid callable");
        }

        $option = $this;

        return function ($parameters = null) use ($callable, $options, $option) {
            $connection = call_user_func($callable, $options, $parameters);

            if (!$connection instanceof AggregateConnectionInterface) {
                $class = get_class($option);

                throw new \InvalidArgumentException("$class expects a valid connection type returned by callable initializer");
            }

            return $connection;
        };
    }
protected function getConnectionInitializer(OptionsInterface $options, $callable)
    {
        if (!is_callable($callable)) {
            $class = get_called_class();

            throw new \InvalidArgumentException("$class expects a valid callable");
        }

        $option = $this;

        return function ($parameters = null) use ($callable, $options, $option) {
            $connection = call_user_func($callable, $options, $parameters);

            if (!$connection instanceof AggregateConnectionInterface) {
                $class = get_class($option);

                throw new \InvalidArgumentException("$class expects a valid connection type returned by callable initializer");
            }

            return $connection;
        };
    }
Wraps a callable to ensure that the returned value is a valid connection.

@param OptionsInterface $options  Client options.
@param mixed            $callable Callable initializer.

@return \Closure