Re: [boost] [finally] early draft available

From: David Abrahams (dave_at_[hidden])
Date: 2006-03-09 11:57:22

Alexander Nasonov <alnsn-boost_at_[hidden]> writes:

> In short, BoostCandidate.Finally is a (better, in my opinion) replacement both
> for try-finally block and for ScopeGuard.
> It can be used when RAII approach is not quite applicable. Typical example is
> VectorInserter class in ScopeGuard article by Andrei Alexandrescu and Petru
> Marginean ( http://tinyurl.com/26vzp ).
>
> Below is a comparison with ScopeGuard approach (typeof registration is omitted
> for brevity).
>
>  // code snipset copied from ScopeGuard article:
>  void User::AddFriend(User& newFriend)
>  {
>      friends_.push_back(&newFriend);
>      ScopeGuard guard = MakeObjGuard(
>          friends_, &UserCont::pop_back);
>      pDB_->AddFriend(GetName(), newFriend.GetName());
>      guard.Dismiss();
>  }
>
>
>  // First form of BoostCandidate.Finally
>  void User::AddFriend(User& newFriend)
>  {
>      friends_.push_back(&newFriend);
>      bool dismiss = false;
>      BOOST_FINALLY_BEGIN( (friends_)(dismiss) )
>      {
>          if(!dismiss)
>              friends_.pop_back();
>      } BOOST_FINALLY_END;
>      pDB_->AddFriend(GetName(), newFriend.GetName());
>      dismiss = true;
>  }

How, exactly, is this an improvement on ScopeGuard?  It's longer and
more complicated, I'll give you that, but those are not usually
thought of as virtues.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com