Boost C++ Application Development Cookbook - Second Edition

Converting smart pointers

Here's a problem:

1. You have a class named some_class:

struct base {    virtual void some_methods() = 0;    virtual ~base();}; struct derived: public base {    void some_methods() /*override*/;    virtual void derived_method() const;        ~derived() /*override*/;};

2. You have a third-party API that returns constructed derived by shared pointer to base and accepts shared pointer to const derived in other functions:

#include <boost/shared_ptr.hpp>boost::shared_ptr<const base> construct_derived();void im_accepting_derived(boost::shared_ptr<const derived> p);

3. You have to make the following code work:

void trying_hard_to_pass_derived() {    boost::shared_ptr<const base> d = construct_derived();    // Oops! Compile time error: // ‘const struct ...