C++ inheritance and casting problems

Asked Apr 04 '21 at 15:11

Active Apr 04 '21 at 15:23

Viewed 26 times

So I have this class and struct:

class ISDFParams
{
public:
    virtual ~ISDFParams() = default;
    Vector3 point;
};

struct SDFSphereParams : public ISDFParams {
public:
    float radius;
};

I use it later like this

SDFSphereParams p;
p.radius = 4;

GetDensityData(p);

In GetDensityData(ISDFParams sdfParams) I do

SDFSphereParams* _params = (SDFSphereParams*)&params;

The problem is when I print _params->radius its anything else but 4.

What am I doing wrong?

P.S. I know the example is a bit pointless, but the original code is rather long so I cut down it my problem.

edited Apr 04 '21 at 15:23

asked Apr 04 '21 at 15:11

trshmanx

you are trying to copy construct base class object using derived class variable. `GetDensityData(ISDFParams sdfParams)` method actually copies `ISDFParams` part of your object hence it does not contain derived class variable `radius` hence it prints garbage value. – Mital Vora Apr 04 '21 at 15:17
That can't be right? `_params` is a pointer. So you have to use `_params->radius`. You also don't actually show how you are displaying the value. – Andrew Truckle Apr 04 '21 at 15:17
Change `GetDensityData` to take the object by reference – Alan Birtles Apr 04 '21 at 15:19
@AndrewTruckle yes I do with ->, wrote by mistake – trshmanx Apr 04 '21 at 15:23
@AlanBirtles can you write answer. I don't understand what you mean. – trshmanx Apr 04 '21 at 15:25
He can’t write an answer as your question was closed. – Andrew Truckle Apr 04 '21 at 15:49
Search passing by reference. It is very easy. – Andrew Truckle Apr 04 '21 at 15:50

C++ inheritance and casting problems

0 Answers0