C++ - Smart Pointers - Passing derived class shared pointer to base through template

Question

I have the following and having difficulty resolving the error please help.

i have the following class as template definition somewhere.

template<class ConcreteHandlerType>
class SomeAcceptor: public ACE_Acceptor<ConcreteHandlerType, ACE_SOCK_Acceptor>

In some other file, i initialize this class in the constructor

class initialize {

    typedef SomeAcceptor<BaseClassSomeHandler> baseAcceptor_t;
    typedef SomeAcceptor<DerivedClassSomeHandler> derivedAcceptor_t;
    boost::shared_ptr<baseAcceptor_t;> mAcceptor;   
    boost::shared_ptr<derivedAcceptor_t;> mDerivedAcceptor;   

    bool HandleAcceptNotification(BaseClassSomeHandler& someHandler);

    initialize() : mAcceptor(0), mDerivedAcceptor(new DerivedAcceptor_t) {
        mAcceptor->SetAcceptNotificationDelegate(fastdelegate::MakeDelegate(this, &initialize::HandleAcceptNotification));
    }
}

Error i get is

error: no matching function for call to `boost::shared_ptr<SomeAcceptor<BaseClassSomeHandler> >::shared_ptr(int)'common/lib/boost_1_39_0/boost/smart_ptr/shared_ptr.hpp:160: note: candidates are: boost::shared_ptr<SomeAcceptor<BaseClassSomeHandler> >::shared_ptr(const boost::shared_ptr<SomeAcceptor<BaseClassSomeHandler> >&)
common/lib/boost_1_39_0/boost/smart_ptr/shared_ptr.hpp:173: notboost::shared_ptr<T>::shared_ptr() [with T = SomeAcceptor<BaseClassSomeHandler>]

I also tried overloading the function with bool HandleAcceptNotification(DerivedClassSomeHandler& someHandler);

but because mAcceptor is of type SomeAcceptor BaseClassSomeHandler, i get this error, but to fix this.

I guess i need to cast it somehow, but how to do it?

i tried doing like below inside the constructor and it didn't work

    initialize() : mAcceptor(0), mDerivedAcceptor(new DerivedAcceptor_t) {

        mAcceptor = mDerivedAcceptor;   // Error here

        mAcceptor->SetAcceptNotificationDelegate(fastdelegate::MakeDelegate(this, &initialize::HandleAcceptNotification));
    }

score 1 · Accepted Answer · edited May 23 '17 at 12:11

From your code, it looks like you want mAcceptor to be assigned NULL (0), if that is the case you don't need to initialize it at all, as the default constructor will take care of that. But, since you call a function on that (NULL) pointer immediately, its not immediately clear exactly what you want to do.

If you want mAcceptor and mDerivedAcceptor to point to the same (shared) object and assuming DerivedClassSomeHandler is derived from BaseClassSomeHandler, this is a situation where you should use boost::shared_static_cast, as described here.

There's also some good information in this apparently related question.

score 0 · Answer 2 · answered Jul 25 '11 at 17:47

The error is due to the mAcceptor(0) in

initialize() : mAcceptor(0), mDerivedAcceptor(new DerivedAcceptor_t) {
    mAcceptor->SetAcceptNotificationDelegate(fastdelegate::MakeDelegate(this, &initialize::HandleAcceptNotification));
}

The smart_ptr default constructor assigns the wrapped ptr to NULL, so leave out mAcceptor(0) from the initialization list.

score 0 · Answer 3 · answered Jul 25 '11 at 17:49

0

boost::shared_ptr<SomeAcceptor<BaseClassSomeHandler> >::shared_ptr(int)

It's yelling at you that there's no constructor that accepts an int.

Just use: mAcceptor()

answered Jul 25 '11 at 17:49

Yochai Timmer

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C++ - Smart Pointers - Passing derived class shared pointer to base through template

3 Answers3