Update example to use the provided StrongPtr

Author: SSheldon

examples/example.rs

@@ -2,25 +2,9 @@
 extern crate objc;
 
 use objc::Encode;
+use objc::rc::StrongPtr;
 use objc::runtime::{Class, Object};
 
-/// Wrapper around an `Object` pointer that will release it when dropped.
-struct StrongPtr(*mut Object);
-
-impl std::ops::Deref for StrongPtr {
-    type Target = Object;
-
-    fn deref(&self) -> &Object {
-        unsafe { &*self.0 }
-    }
-}
-
-impl Drop for StrongPtr {
-    fn drop(&mut self) {
-        let _: () = unsafe { msg_send![self.0, release] };
-    }
-}
-
 fn main() {
     // Get a class
     let cls = class!(NSObject);
@@ -36,13 +20,13 @@ fn main() {
     let obj = unsafe {
         let obj: *mut Object = msg_send![cls, alloc];
         let obj: *mut Object = msg_send![obj, init];
-        StrongPtr(obj)
+        StrongPtr::new(obj)
     };
-    println!("NSObject address: {:p}", &*obj);
+    println!("NSObject address: {:p}", obj);
 
     // Access an ivar of the object
     let isa: *const Class = unsafe {
-        *obj.get_ivar("isa")
+        *(**obj).get_ivar("isa")
     };
     println!("NSObject isa: {:?}", isa);
 
@@ -55,7 +39,7 @@ fn main() {
 
     // Invoke a method on the object
     let hash: usize = unsafe {
-        msg_send![obj, hash]
+        msg_send![*obj, hash]
     };
     println!("NSObject hash: {}", hash);
 }