I have a class constructor that expects a reference to another class object to be passed in as an argument. I understand that references are preferable to pointers when no pointer arithmetic will be performed or when a null value will not exist.

This is the header declaration of the constructor:

class MixerLine {

private:
    MIXERLINE _mixerLine;

public:

    MixerLine(const MixerDevice& const parentMixer, DWORD destinationIndex); 

    ~MixerLine();
}

This is the code that calls the constructor (MixerDevice.cpp):

void MixerDevice::enumerateLines() {

    DWORD numLines = getDestinationCount();
    for(DWORD i=0;i<numLines;i++) {

        MixerLine mixerLine( this, i );
        // other code here removed
    }
}

Compilation of MixerDevice.cpp fails with this error:

Error 3 error C2664: 'MixerLine::MixerLine(const MixerDevice &,DWORD)' : cannot convert parameter 1 from 'MixerDevice *const ' to 'const MixerDevice &'

But I thought pointer values could be assigned to pointers, e.g.

Foo* foo = new Foo();
Foo& bar = foo;