Question: I just found that there's no LinkedList implementation in Objective-C, but I need one. So I am going to use `std::list`(or there's a better alternative?).

My question is: what should I care about memory management under ARC and non-ARC?

Answer: 
Example of ensuring that the owning side (Service) always gets updated.

```
class ServiceGroup
{
    public function addService($service)
    {
        if (!$service) return;

        $this->services[] = $service;
        $service->addGroup($this);
    }
}

```
i've done it like this: 

<http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/association-mapping.html#many-to-many-bidirectional>

and this works like a charm