Re: [boost] Interest in non-intrusive signal/slot lib?

20 May 2015

      Le 12/05/15 04:25, Emil Dotchevski a écrit :
...
Hello,
I realize that Boost has Signals library already, but I've implemented a
non-intrusive one which approaches the problem differently, and I'm pretty
sure that there is no overlap between the two. It turned out more generic
than I originally anticipated, so I thought I'd ask if others would find it
useful as well.
I have some concerns about the lifetime of the emitters.

E.g. an application can have a class that contains a several possible 
emitters. The lifetime of all the emitters depends on the lifetime of 
the C instance.

struct C {
     T1 e1;
     T2 e2;
};

int main() {

     shared_ptr<C> c = make_shared<C>();
     // ...

The lifetime of emitters c->e1 and c->e2 is managed by c.

Now I would like to connect to c->e1 and/or c->e2. But I would need to 
change the class C, as I don't have a shared_ptr to &(c->e1) or &(c->e2).

Do you have a solution without changing C? If not, could your library 
take care of this use case? IMO this will reduce the need for more 
shared_ptr than really needed.

Maybe a connect_member

auto c1 = connect_member(c , ...);
auto c2 = connect_member(c, ...);

or splitting the responsabilities of emitter lifetime tracker and the 
emitter itself

auto c1 = connect(c, c->e1, ...);
auto c2 = connect(c, c->e2, ...);

Maybe having a smart pointer that give access to a member pointer of a 
shared_ptr/weak_ptr

template 
class member_shared_ptr;
template 
class member_weak_ptr;

could allow to overload the connect function

auto c1 = connect(member_shared_ptr(c), ...);
auto c2 = connect(member_shared_ptr(c), ...);

The class C could be defined as follows to make explicit that the 
instances are shared and provide access to shared emitters

struct C : shared_from_this {
     T1 e1_;
     T2 e2_;
public:
     shared_ptr<C> make();
     member_shared_ptr e1_emitter() { return 
member_shared_ptr(share_from_this()); }
     member_shared_ptr e2_emitter(){ return 
member_shared_ptr(share_from_this()); }
};

auto c = C::make();
auto c1 = connect(c->e1_emitter(), ...);
auto c2 = connect(c->e2_emitter(), ...);

Vicente

Re: [boost] Interest in non-intrusive signal/slot lib?

Vicente J. Botet Escriba