Add Id::as_ptr helper function

Author: madsmtm

objc2/CHANGELOG.md

@@ -11,7 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   upgrading easier.
 * Allow using `From`/`TryFrom` to convert between `rc::Id` and `rc::WeakId`.
 * Added `Bool::as_bool` (more descriptive name than `Bool::is_true`).
-* Added convenience method `Id::new_null`.
+* Added convenience methods `Id::new_null` and `Id::as_ptr`.
 
 
 ## 0.3.0-alpha.6 - 2022-01-03

objc2/src/exception.rs

@@ -68,7 +68,7 @@ extern "C" {
 #[inline]
 pub unsafe fn throw(exception: Option<&Id<Object, Shared>>) -> ! {
     let exception = match exception {
-        Some(id) => &**id as *const Object as *mut ffi::objc_object,
+        Some(id) => id.as_ptr() as *mut ffi::objc_object,
         None => ptr::null_mut(),
     };
     unsafe { ffi::objc_exception_throw(exception) }

objc2/src/message/mod.rs

@@ -252,8 +252,7 @@ unsafe impl<T: Message + ?Sized> MessageReceiver for NonNull<T> {
 unsafe impl<T: Message + ?Sized, O: Ownership> MessageReceiver for Id<T, O> {
     #[inline]
     fn as_raw_receiver(&self) -> *mut Object {
-        // TODO: Maybe don't dereference here, just to be safe?
-        (&**self).as_raw_receiver()
+        self.as_ptr() as *mut Object
     }
 }
 
@@ -449,7 +448,7 @@ mod tests {
         };
         assert_eq!(result, 4);
 
-        let obj: *const ManuallyDrop<Object> = (&**obj as *const Object).cast();
+        let obj: *const ManuallyDrop<Object> = obj.as_ptr().cast();
         let result: u32 = unsafe { msg_send![obj, foo] };
         assert_eq!(result, 4);
     }

objc2/src/rc/id.rs

@@ -187,6 +187,19 @@ impl<T: Message + ?Sized, O: Ownership> Id<T, O> {
         // SAFETY: Upheld by the caller
         NonNull::new(ptr).map(|ptr| unsafe { Id::new(ptr) })
     }
+
+    /// Returns a raw pointer to the object.
+    ///
+    /// The pointer is valid for at least as long as the `Id` is held.
+    #[inline]
+    pub fn as_ptr(&self) -> *mut T {
+        // Note: This is not an associated function, which breaks the
+        // guideline that smart pointers shouldn't add inherent methods!
+        //
+        // However, this method is quite useful when migrating old codebases,
+        // so I think we'll let it be here for now.
+        self.ptr.as_ptr()
+    }
 }
 
 // TODO: Add ?Sized bound
@@ -246,7 +259,7 @@ impl<T: Message, O: Ownership> Id<T, O> {
         // retained objects it is hard to imagine a case where the inner type
         // has a method with the same name.
 
-        let ptr = ManuallyDrop::new(self).ptr.as_ptr() as *mut ffi::objc_object;
+        let ptr = ManuallyDrop::new(self).as_ptr() as *mut ffi::objc_object;
         // SAFETY: The `ptr` is guaranteed to be valid and have at least one
         // retain count.
         // And because of the ManuallyDrop, we don't call the Drop

objc2/src/rc/weak_id.rs

@@ -40,7 +40,7 @@ impl<T: Message> WeakId<T> {
         // allow loading an `Id<T, Shared>` later on.
 
         // SAFETY: `obj` is valid
-        unsafe { Self::new_inner(&**obj as *const T as *mut T) }
+        unsafe { Self::new_inner(obj.as_ptr()) }
     }
 
     /// # Safety