Add ClassType::as_super and ClassType::as_super_mut

Author: madsmtm

objc2/examples/class_with_lifetime.rs

@@ -117,6 +117,14 @@ unsafe impl<'a> ClassType for MyObject<'a> {
 
         Class::get("MyObject").unwrap()
     }
+
+    fn as_super(&self) -> &Self::Super {
+        &self.superclass
+    }
+
+    fn as_super_mut(&mut self) -> &mut Self::Super {
+        &mut self.superclass
+    }
 }
 
 fn main() {

objc2/src/class_type.rs

@@ -17,7 +17,8 @@ use crate::Message;
 /// # Safety
 ///
 /// The class returned by [`Self::class`] must be a subclass of the class that
-/// [`Self::Super`] represents.
+/// [`Self::Super`] represents, and `as_super`/`as_super_mut` must be
+/// implemented correctly.
 ///
 /// In pseudocode:
 /// ```ignore
@@ -78,4 +79,12 @@ pub unsafe trait ClassType: Message {
     /// class, e.g. if the program is not properly linked to the framework
     /// that defines the class.
     fn class() -> &'static Class;
+
+    /// Get an immutable reference to the superclass.
+    // Note: It'd be safe to provide a default impl using transmute here if
+    // we wanted to!
+    fn as_super(&self) -> &Self::Super;
+
+    /// Get a mutable reference to the superclass.
+    fn as_super_mut(&mut self) -> &mut Self::Super;
 }

objc2/src/foundation/object.rs

@@ -22,6 +22,14 @@ unsafe impl ClassType for NSObject {
     fn class() -> &'static Class {
         class!(NSObject)
     }
+
+    fn as_super(&self) -> &Self::Super {
+        &self.__inner
+    }
+
+    fn as_super_mut(&mut self) -> &mut Self::Super {
+        &mut self.__inner
+    }
 }
 
 extern_methods!(

objc2/src/macros/declare_class.rs

@@ -454,6 +454,16 @@ macro_rules! declare_class {
                 // We just registered the class, so it should be available
                 $crate::runtime::Class::get(stringify!($name)).unwrap()
             }
+
+            #[inline]
+            fn as_super(&self) -> &Self::Super {
+                &self.__inner
+            }
+
+            #[inline]
+            fn as_super_mut(&mut self) -> &mut Self::Super {
+                &mut self.__inner
+            }
         }
 
         // Methods

objc2/src/macros/extern_class.rs

@@ -259,6 +259,16 @@ macro_rules! __inner_extern_class {
             fn class() -> &'static $crate::runtime::Class {
                 $crate::class!($name)
             }
+
+            #[inline]
+            fn as_super(&self) -> &Self::Super {
+                &self.__inner
+            }
+
+            #[inline]
+            fn as_super_mut(&mut self) -> &mut Self::Super {
+                &mut self.__inner
+            }
         }
     };
     (

tests/src/test_object.rs

@@ -26,6 +26,14 @@ unsafe impl ClassType for MyTestObject {
     fn class() -> &'static Class {
         class!(MyTestObject)
     }
+
+    fn as_super(&self) -> &Self::Super {
+        &self.inner
+    }
+
+    fn as_super_mut(&mut self) -> &mut Self::Super {
+        &mut self.inner
+    }
 }
 
 impl MyTestObject {