On Sat, Mar 27, 2010 at 02:37:37AM +0800, PCMan wrote: > On Sat, Mar 27, 2010 at 12:17 AM, Julian Andres Klode <j...@jak-linux.org> > wrote: > > Well, than f_finish() should probably not be there in the Volume > > interface; so I think that's a bug. > So how can I fix this? Ship with a custom glib vapi file and remove > *_finish from GVolume? Will this work? Or, can you make automatic > generation of *_finish optional in Vala, or make the automatically > generated *_finish override the abstract method in parent interface if > its found? It's a bug: https://bugzilla.gnome.org/show_bug.cgi?id=614045
> > >> For the second question, if I want to return a unowned GList, it has > >> to be owned by the class and cannot be a local variable, right? Would > >> you please add this to vala tutorial? I found it not documented and > >> this behavior is not easy to figure out. In addition, this is not > >> consistent with GObject with C. In C we can create a new GList and > >> return it without the need to make it owned by anyone. The callee of > >> the function is responsible to free the list. > > > > Because the list is unowned in can not be local, as it would go > > away once the function returns. If you want to return a locally > > created object, the return value can only be owned. > This is quite different from C and C++ and is hard to understand for a > C programmer I think. No, it's not. The difference is just that instead of manually freeing the returned pointer, the return values are marked as unowned/owned, and Vala then adds code to free owned values automatically. In short, if you have to free a return value in C, it is owned; if you don't have to free it, it is unowned. > However, I don't get it. Let take GVolumeMonitor::get_volumes as example. > It returns unowned GLib.List. So if I want to implement that, I should > create a list and make it owned by the object instance and then return > it unowned. However this is slightly different from the behavior of > glib in C. In C GVolumeMonitor::get_volumes returns a > "newly-allocated" GList containing a list of GObjects. The caller is > responsible to g_list_foreach(list, g_object_unref, NULL); and then > g_list_free(list); So, the problem is that the function return values are falsely marked as unowned in the VAPI. I reported a bug for it at https://bugzilla.gnome.org/show_bug.cgi?id=614044 > However, with Vala, how can I make vala methods return a "newly > allocated GList" with all objects in it having increased ref_count? > Automatic ref couting management in Vala is handy if you only use it > in Vala but I find it difficult to make things right when interfacing > with C code. I need to check the generated C code to see if it does > what I really want. Any better guide for this? Already read Vala > tutorial, but I still haven't get it. Just don't mark the list as unowned. -- Julian Andres Klode - Debian Developer, Ubuntu Member See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/.
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