Re: [Boost-users] pimpl and Qt

From: Arne Vogel (Arne.Vogel_at_[hidden])
Date: 2005-05-19 05:10:04

Vladimir Krasovsky wrote:

>Hello Arne,
>
>
>  
>
>>scoped_ptr cannot be used with incomplete types, unfortunately, and thus
>>is not available for use in the pimpl idiom.
>>    
>>
>
>Please read http://www.boost.org/libs/smart_ptr/scoped_ptr.htm . Near
>the end of page you can see
>"One common usage of scoped_ptr is to implement a handle/body (also
>called pimpl) idiom which avoids exposing the body (implementation) in
>the header file."
>
>Examples are also there.
>  
>

Hello Vladimir,

I stand corrected. So it's actually not "scoped_ptr cannot be used with 
incomplete types"
but "scoped_ptr's destructor cannot be instantiated with incomplete types".

So

class UsingPimpl {
private:
    struct Impl;
    boost::scoped_ptr<Impl> impl;

public:
    UsingPimpl();

    void doSomething();
};

won't work, but by adding UsingPimpl's destructor declaration (to 
inhibit automatic generation) to the
definition of UsingPimpl, and the destructor's definition (after 
UsingPimpl::Impl has been defined) to
the implementation file, it can be made to work.

Thanks a lot,
Arne Vogel