Re: [Boost-users] [Iostreams] Safely returning filtering_istream from function

Subject: Re: [Boost-users] [Iostreams] Safely returning filtering_istream from function
From: Larry Evans (cppljevans_at_[hidden])
Date: 2013-06-05 11:49:47

On 06/05/13 07:37, Szymon Gatner wrote:
> Hi,
> 
> I would like to return filtering_istream via
> std::unique_ptr<std::iostream> so that client code can just use iostream
> interface without knowing what is actual stream type.
> 
> Inside the factory function filtering_istream is prepared with possible
> filters attached. Problem is filters are attached by reference. My
> question is: how to elegantly attach filters to a filtering_istream so
> that they live as long as filtering_istream itself? How to attach a
> filter via shared_ptr for example?
> 
> Regards,
> Szymon Gatner
> 
> 
Hi Szymon,

Could you not create a derived version of filtering_istream where
the 1st base class contained all the filters and the 2nd base
class was a filtering_istream.  Then, I'd guess you could just
pass references to filters in 1st base class to the 2nd base
class, and they would live *almost* as long as the 2nd base
class.  I say almost because the 1st base class would be
destroyed 1st.  Would that be a problem?  Hmm.  Maybe the
1st base could be just a wrapped pointer which would be
deleted in the derived class?

-regards,
Larry