objc_bridge.rs

use std::libc;
use std::cast::transmute;

type Id = libc::uintptr_t;
type Sel = libc::uintptr_t;

#[link(name = "objc")]
extern {
    fn sel_registerName(sel: &str) -> Sel;
    fn objc_msgSend(object: Id, sel: Sel, ...) -> libc::uintptr_t;
    fn objc_lookUpClass(name: &str) -> Id;
}

trait ObjcObject {
    fn send<T>(&self, sel: &str) -> T;
}
impl ObjcObject for Id {
    fn send<T>(&self, sel: &str) -> T {
        let sel_ = unsafe { sel_registerName(sel) };
        let imp: extern "C" fn(Id, Sel, ...) -> T = unsafe { std::cast::transmute(objc_msgSend) };
        imp(*self, sel_)
    }
}

fn objc_class(name: &str) -> Id {
    println!("Looking up {}", name);
    unsafe { objc_lookUpClass(name) }
}

fn main() {
    let kls = objc_class("NSObject");
    let hash: uint = kls.send("hash");
    let instance: Id = kls.send("alloc");
    println!("NSObject={} +[NSObject hash]={} +[NSObject alloc]={}", kls, hash, instance);
}