WIP: Add API for associated objects

crates/objc2/src/macros/associated_object.rs

@@ -0,0 +1,24 @@
+macro_rules! associated_object {
+    (
+        $(#[$m:meta])*
+        impl $name:ident {
+            $v_getter:vis fn $getter_name:ident(&self) -> $getter_ty:ty;
+            $v_setter:vis fn $setter_name:ident(&self, $setter_param:ident: $setter_ty:ty);
+        }
+    ) => {
+        const _: () = {
+            static mut __KEY: u8 = 0;
+
+            $(#[$m])*
+            impl $name {
+                $v_getter fn $getter_name(&self) -> $getter_ty {
+
+                }
+
+                $v_setter fn $setter_name(&self, $setter_param: $setter_ty) {
+
+                }
+            }
+        }
+    };
+}

crates/objc2/src/macros/mod.rs

@@ -6,6 +6,7 @@ mod __rewrite_self_arg;
 mod declare_class;
 mod extern_class;
 mod extern_methods;
+mod associated_object;
 mod extern_protocol;
 
 /// Gets a reference to an [`AnyClass`] from the given name.

crates/objc2/src/runtime/associated_object.rs

@@ -0,0 +1,90 @@
+use core::ptr;
+
+use super::Object;
+use crate::rc::{Id, Shared};
+use crate::ffi;
+
+/// Associated object support.
+///
+/// These are associated functions, since they are very rarely used, and will
+/// mostly just clutter up the `Deref` chain and documentation of all other
+/// classes in `icrate`.
+///
+/// See [Apple's documentation](https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocAssociativeReferences.html).
+impl Object {
+    ///
+    ///
+    /// # Panics
+    ///
+    /// This may panic or abort the process if the specified object does not
+    /// support associated objects.
+    unsafe fn set_associated_ptr<K>(this: &Self, key: &K, value: *const ()) {
+        let key: *const K = key;
+        // SAFETY: The object and key is non-null
+        //
+        // Caller ensures that the key is uniquely used for the expected
+        // operation.
+        unsafe {
+            ffi::objc_setAssociatedObject(this.as_ptr(), key.cast(), value as *mut _, ffi::OBJC_ASSOCIATION_ASSIGN)
+        }
+    }
+
+    unsafe fn set_associated_id<K, T>(this: &Self, key: &K, value: Option<&Id<T, Shared>>) {
+        let key: *const K = key;
+        let ptr: *const T = value.map(|value| Id::as_ptr(value)).unwrap_or(ptr::null());
+        // SAFETY: The object and key is non-null, and the value came from
+        // a shared `Id`, so it is safe to retain.
+        //
+        // Caller ensures that the key is uniquely used for the expected
+        // operation.
+        unsafe {
+            ffi::objc_setAssociatedObject(
+                this.as_ptr(),
+                key.cast(),
+                ptr.cast(),
+                ffi::OBJC_ASSOCIATION_RETAIN,
+            )
+        }
+    }
+
+    unsafe fn get_associated_ptr<K>(this: &Self, key: &K) -> *const () {
+        let key: *const K = key;
+        // SAFETY:
+        unsafe { ffi::objc_getAssociatedObject(this.as_ptr(), key.cast()).cast() }
+    }
+
+    unsafe fn get_associated_id<K, T>(this: &Self, key: &K) -> Id<T, Shared> {
+        let ptr = this.get_associated_ptr(key) as *mut T;
+        // SAFETY: Caller upholds that the associated object stores an `Id`,
+        // and that the `Id` was originally `Shared`.
+        unsafe { Id::retain_autoreleased(ptr) }
+    }
+
+    unsafe fn remove_associated<K, T>(this: &Self, key: &K) {
+        let key: *const K = key;
+        // SAFETY: The object and key is non-null, and the associated is being
+        // broken, so the policy doesn't matter.
+        //
+        // Caller ensures that the key is uniquely used for the expected
+        // operation.
+        unsafe {
+            ffi::objc_setAssociatedObject(
+                this.as_ptr(),
+                key.cast(),
+                ptr::null(),
+                ffi::OBJC_ASSOCIATION_ASSIGN,
+            )
+        }
+    }
+
+    fn remove_all_associated(this: &Self) {
+        // SAFETY:
+        unsafe { ffi::objc_removeAssociatedObjects(this.as_ptr()) }
+    }
+
+    // objc_setAssociatedObject
+    // objc_getAssociatedObject
+    // objc_removeAssociatedObjects
+
+    // https://nshipster.com/associated-objects/
+}

crates/objc2/src/runtime/mod.rs

@@ -1265,10 +1265,6 @@ impl AnyObject {
         // SAFETY: Invariants upheld by caller
         unsafe { *self.ivar_mut::<T>(name) = value };
     }
-
-    // objc_setAssociatedObject
-    // objc_getAssociatedObject
-    // objc_removeAssociatedObjects
 }
 
 impl fmt::Debug for AnyObject {