Jani, ok what you want to do is quite a lot more intrusive, so you need some more involved methods, but it should be possible. I would do it by noting the following - data_1 is published to python as a boost::shared_ptr<Data> (default holder type) - usually it is difficult for a class member function, to obtain a shared_ptr<> to itself, i.e. something like `this` but not of type Data* but of boost::shared_ptr<Data>. - fortunately there is something supported by boost itself, called `enable_shared_from_this`, see http://stackoverflow.com/questions/142391/getting-a-boostshared-ptr-for-this - Now you want `owner` to hold on to this `shared_ptr<Data>` which ensures that `data_1` does not get deleted before `owner`, you can do this by owner->setData( shared_from_this() ) in any member function of `Data`. - Note that I _think_ that you are not allowed to use `shared_from_this()` in the constructor itself, so you might have to use boost::pythons `make_constructor` to make an ordinary member / non-member function behave as the constructor in python.
Maybe someone has a quicker way of doing this, but remember that this is exactly the use case that `shared_ptr` are made for, Holger On Thu, Jul 5, 2012 at 6:47 PM, Jani Tiainen <rede...@gmail.com> wrote: > I want to do it another way around: > > Instance of Owner should hold reference to data_1 and data_2 as long as > owner is alive. > > Now following happens: > owner = Owner() > data_1 = Data(owner) # data_1 ownership is transferred to owner object > data_2 = Data(owner) # data_2 ownership is transferred to owner object > > print owner.get_data_objects() > > <data_1>, <data_2> > > del data_1 > del data_2 > > print owner.get_data_objects() > # Crash because data_1 and data_2 are deleted even owner should still hold > the reference. > > I tried to do it like > http://www.boost.org/doc/libs/1_49_0/libs/python/test/injected.cpp but it > didn't worked for me. > > > On Thu, Jul 5, 2012 at 7:00 PM, John Reid <j.r...@mail.cryst.bbk.ac.uk> > wrote: >> >> On 05/07/12 11:49, Jani Tiainen wrote: >> > Hi, >> > >> > I'm new to python.boost library and I'm trying to use it to wrap a third >> > party library. Everything else I've managed to get working - thanks to >> > excellent library and lot of examples I've found around a net. >> > >> > Only thing I can't get working properly is instance ownership transfer >> > in constructor. >> > >> > So classes in library are defined like follows: >> > >> > class Owner { >> > ... >> > } >> > >> > class Data { >> > Data(Owner *owner); // <-- Here happens ownership transfer. >> > } >> > >> > >> > Python code is like follows: >> > >> > owner = Owner() >> > data_1 = Data(owner) >> > data_2 = Data(owner) >> > >> > So when Python script stops runnning it causes crash due the fact that >> > I've data objects are automatically destroyed by Owner-class but Python >> > deletes them by using Data-class destructor (which shouldn't happen >> > ever). >> > >> >> If I understand you correctly then you want the owner object to remain >> alive at least as long as data_1 and data_2? If so you could use >> with_custodian_and_ward: >> >> http://www.boost.org/doc/libs/1_49_0/libs/python/doc/v2/with_custodian_and_ward.html >> >> For example something like the following should work: >> >> namespace py = boost::python; >> py::class_< >> ... >> > my_class( >> "Data", >> "docstring.", >> py::init< Owner * >( "Constructor." )[ >> py::with_custodian_and_ward< 1, 2 >() >> ] >> ); >> >> _______________________________________________ >> Cplusplus-sig mailing list >> Cplusplus-sig@python.org >> http://mail.python.org/mailman/listinfo/cplusplus-sig > > > > > -- > Jani Tiainen > > - Well planned is half done, and a half done has been sufficient before... > > > _______________________________________________ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > http://mail.python.org/mailman/listinfo/cplusplus-sig _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
