Le 30 juil. 2013 à 10:27, Vincent Habchi <vi...@macports.org> a écrit :
> Rick, > > thanks for answering, because what I found on the Internet seems > contradictory. Some say that if the C function is placed inside the > implementation block, then it can access attributes as if it were a true > Obj-C method; some say otherwise. So it’s a bit difficult to find a > definitive answer thereon. If it is in the implementation block, you can access all private ivar and property, but only if you have a reference to self in the first place. For instance, you can have this: @implementation Foo { id privateVar; } static inline void internalInlineFunction(Foo *self) { // do something with self->privateVar. } - (void)publicMethod { internalInlineFunction(self); } @end I'm using this trick when I need inline code (something that can't be done with Obj-C method), but for a callback, I would rather just keep it simple and simply call a method to handle it. @implementation Foo static void callback(void *ctxt) { // Sidenote; 'self' is a reserved keyword only inside Obj-C method body. You can use it freely elsewhere, and it does not have special meaning. // that's why you have to pass it as explicit parameter. Foo *self = (Foo *)ctxt; [self handleCallback]; } - (void)handleCallback { // } @end > >> Having said that, most callback APIs allow you to pass a context parameter >> that gets passed back to your C callback. Often times, this context >> parameter is a void* you pass in along with a pointer to your callback >> function. You can pass "self" in this parameter when you register the >> callback, then cast it inside your callback back to MyClass* (or whatever >> your class is). > > Yes, right; it’s a SQLite callback, the first parameter is a void *. I wanted > to pass a pointer to a structure containing both a unique query id (out of > uuid) and a pointer to self, but got told off by ARC because it apparently > forbids to embed pointers to Obj-C objects in C-structs. So I just > bridge-cast it to void *. > > Assuming the pointer to the struct is named ‘info’ and the field containing a > reference to ‘self’ is called ‘this’, [info->this someMethod] as well as > info->this->someAttribute are legal, aren’t they? > > Thanks a lot! > Vincent > > > _______________________________________________ > > Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/cocoa-dev/devlists%40shadowlab.org > > This email sent to devli...@shadowlab.org -- Jean-Daniel _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com