[Qt-interest] Const correctness with QSharedPointer

[Colin Kern]

On Mon, Dec 7, 2009 at 4:31 PM, Stephen Jackson <spjackson42 at gmail.com> wrote:
> 2009/12/7 Brad Howes :
>> On Dec 7, 2009, at 3:31 PM, Colin Kern wrote:
>>
>>> I want to pass a QSharedPointer to a function as a const pointer, so
>>> that the compiler will enforce that I don't mutate the object the
>>> shared pointer is pointing to.  Can I do this with "void func(const
>>> QSharedPointer<A> p);" or does that just enforce that I won't change
>>> what the shared pointer is pointing to?

I'm going to hijack my own thread here, since I have another question
about QSharedPointers.  Is there a way to maintain polymorphism when
using QSharedPointers?  This code works:

class A { };
class B : public A { };
void func(A* p) { };
int main()
{
    B *p = new B();
    func(p);
}

but this doesn't compile:

#include <QSharedPointer>
class A { };
class B : public A { };
void func(QSharedPointer<A> p) { };
int main()
{
    QSharedPointer<B> p(new B());
    func(p);
}


Thanks,
Colin