"vicente.botet" <vicente.botet@wanadoo.fr> writes:
From: "vicente.botet" <vicente.botet@wanadoo.fr>
Currently the wait callback parameter is either a promise or packaged_task template<typename F> void set_wait_callback(F f);
prom.set_wait_callback(f); // will call f(&prom) task.set_wait_callback(f); // will call f(&task)
I would like to have a wait callback with a user specific parameter. template<typename F,typename U> void set_wait_callback(F f,U* u); // will call f(u)
prom.set_wait_callback(f, x); // will call f(x)
The use case is a class that contains a promise and wants to provide a set_wait_callback. Which parameter will have the wait calback? A promise. But the user is not aware that my class has promise, and he will surely want to have as parameter a pointer to my class. So the simpler is to provide a user specific parameter that is defaulted to instance providing the wait_callback setting.
Of course my class can wrap the user function and the class instance
template <typename R> class X { template <typename F> static void wait_callback_wrapper(promise<R>* p, F f, X*x) { f(x); }
template<typename F> void set_wait_callback(F f) { prom_.set_wait_callback(bind(wait_callback_wrapper, _1, f, this)); } };
But this implies much more resources, two binds instead of one. Could this be added without to much trouble?
It could, but....
Anthony, I've find this on one your posts:
At the moment, I've specified the callbacks as taking a non-const reference to the promise or packaged_task for which they are set, but I'm open to just making them be any callable function, and leaving it up to the user to call bind() to do that.
Anthony, I think that just a callable function will be the best option.
.... I think this is the best option. Anthony -- Anthony Williams | Just Software Solutions Ltd Custom Software Development | http://www.justsoftwaresolutions.co.uk Registered in England, Company Number 5478976. Registered Office: 15 Carrallack Mews, St Just, Cornwall, TR19 7UL