How to pass a Rust function as a selector?

[ghostman2013]

Hello!

I use a little modified code that's based on examples from objc2-app-kit crate sources:

impl AppDelegate {
    fn new(mtm: MainThreadMarker, menu: Option<Menu>) -> Id<Self> {
        let this = mtm.alloc();
        let this = this.set_ivars(Ivars {
            mtm,
            menu,
        });
        unsafe { msg_send_id![super(this), init] }
    }

    fn build_menu(&self, menu: &Menu, ns_menu: &Id<NSMenu>) {
        let ivars = self.ivars();
        for item in menu.items.iter() {
            let ns_menu_item = NSMenuItem::new(ivars.mtm);
            let title = NSString::from_str(&item.name);
            unsafe { ns_menu_item.setTitle(&title) };
            
            if let Some(on_click) = &item.on_click {
                unsafe { ns_menu_item.setAction(Some(on_click)) };
            }

            if let Some(submenu) = &item.submenu {
                let ns_submenu = NSMenu::new(ivars.mtm);
                self.build_menu(submenu, &ns_submenu);
                ns_menu_item.setSubmenu(Some(&ns_submenu));
            }
            
            ns_menu.addItem(&ns_menu_item);
        }
    }

    fn create_menu(&self, application: Id<NSApplication>) {
        let ivars = self.ivars();
        if let Some(menu) = &ivars.menu {
            let main_menu = NSMenu::new(ivars.mtm);
            application.setMainMenu(Some(&main_menu));

            self.build_menu(menu, &main_menu);
        }
    }
}

Just a trivial AppDelegate with menu builder. However, I hit troubles at this step:

if let Some(on_click) = &item.on_click {
    unsafe { ns_menu_item.setAction(Some(on_click)) };
}

The on_click: fn() is a typical Rust function but I can't get how to pass it as a selector, to NSMenuItem called it on click.

Unfortunately, I couldn't find any examples. Could you explain, please, how I can make it?

[madsmtm]

This is a common pattern used in Apple's frameworks, see the documentation on Target-Action, and it's a bit of a pain to handle when you're used to Rust's closures.

There's a similar issue here: #585

Try to have a look at that, in short you have to make a method on your delegate with a selector like onClick:, place it on the menu item with .setAction(Some(sel!(onClick:))) and .setTarget(Some(self)), and then you have to run your click handler in onClick:.

I know that's not a real explanation, but I don't have time to write up a full example right now, will do so later.

[ghostman2013]

This is a common pattern used in Apple's frameworks, see the documentation on Target-Action, and it's a bit of a pain to handle when you're used to Rust's closures.

There's a similar issue here: #585

Try to have a look at that, in short you have to make a method on your delegate with a selector like onClick:, place it on the menu item with .setAction(Some(sel!(onClick:))) and .setTarget(Some(self)), and then you have to run your click handler in onClick:.

I know that's not a real explanation, but I don't have time to write up a full example right now, will do so later.

No, you have explained it very clearly. Thank you! I got how to make.