this is not an lvalue

[Andrey via Digitalmars-d-learn]

On Tuesday, 13 December 2016 at 16:23:16 UTC, Adam D. Ruppe wrote:
> On Tuesday, 13 December 2016 at 15:09:10 UTC, Andrey wrote:
>> void moveTo(ref Parameter parent) {
>
> You probably don't want the `ref` there, nor likely on any 
> other method definitions (especially check removeValue).

Thanks it works, but where should I use the ref? for example in 
C++ I always used pointers for structs, classes in stack etc.:
> void open(const std::string &fileName) {...}