add simple deref macro

gio-subclass/tests/simple_application.rs

@@ -1,6 +1,5 @@
 // adaptation of https://gitlab.gnome.org/GNOME/glib/blob/master/gio/tests/gapplication-example-cmdline2.c
 use std::mem;
-use std::ops;
 use std::ptr;
 use std::sync::{Once, ONCE_INIT};
 
@@ -17,6 +16,8 @@ use glib::prelude::*;
 use glib::translate::*;
 
 extern crate gio_subclass;
+
+#[macro_use]
 extern crate gobject_subclass;
 
 use gio_subclass::application::*;
@@ -127,21 +128,8 @@ glib_wrapper! {
     }
 }
 
-// TODO: This one should probably get a macro
-impl ops::Deref for SimpleApplication {
-    type Target = imp::SimpleApplication;
+gobject_subclass_deref!(SimpleApplication, Application);
 
-    fn deref(&self) -> &Self::Target {
-        unsafe {
-            let base: Application = from_glib_borrow(self.to_glib_none().0);
-            let imp = base.get_impl();
-            let imp = imp.downcast_ref::<imp::SimpleApplication>().unwrap();
-            // Cast to a raw pointer to get us an appropriate lifetime: the compiler
-            // can't know that the lifetime of base is the same as the one of self
-            &*(imp as *const imp::SimpleApplication)
-        }
-    }
-}
 
 impl SimpleApplication {
     pub fn new<'a, I: Into<Option<&'a str>>>(

gobject-subclass/src/deref.rs

@@ -0,0 +1,25 @@
+#[macro_export]
+macro_rules! gobject_subclass_deref(
+    ($name:ident, $base:ident) => {
+        gobject_subclass_deref!($name, imp::$name, $base);
+    };
+
+    ($name:ident, $target:ty, $base:ident) => {
+        use std::ops::Deref;
+
+        impl Deref for $name {
+            type Target = $target;
+
+            fn deref(&self) -> &Self::Target {
+                unsafe {
+                    let base: $base = from_glib_borrow(self.to_glib_none().0);
+                    let imp = base.get_impl();
+                    let imp = imp.downcast_ref::<$target>().unwrap();
+                    // Cast to a raw pointer to get us an appropriate lifetime: the compiler
+                    // can't know that the lifetime of base is the same as the one of self
+                    &*(imp as *const $target)
+                }
+            }
+        }
+    }
+);

gobject-subclass/src/lib.rs

@@ -23,3 +23,6 @@ pub mod guard;
 pub mod properties;
 #[macro_use]
 pub mod object;
+
+#[macro_use]
+mod deref;

gobject-subclass/tests/simple_object.rs

@@ -7,7 +7,6 @@
 // except according to those terms.
 
 use std::mem;
-use std::ops;
 use std::ptr;
 use std::sync::{Once, ONCE_INIT};
 
@@ -19,6 +18,7 @@ extern crate glib;
 use glib::prelude::*;
 use glib::translate::*;
 
+#[macro_use]
 extern crate gobject_subclass;
 use gobject_subclass::object::*;
 
@@ -172,21 +172,7 @@ impl SimpleObject {
     }
 }
 
-// TODO: This one should probably get a macro
-impl ops::Deref for SimpleObject {
-    type Target = imp::SimpleObject;
-
-    fn deref(&self) -> &Self::Target {
-        unsafe {
-            let base: Object = from_glib_borrow(self.to_glib_none().0);
-            let imp = base.get_impl();
-            let imp = imp.downcast_ref::<imp::SimpleObject>().unwrap();
-            // Cast to a raw pointer to get us an appropriate lifetime: the compiler
-            // can't know that the lifetime of base is the same as the one of self
-            &*(imp as *const imp::SimpleObject)
-        }
-    }
-}
+gobject_subclass_deref!(SimpleObject, Object);
 
 #[test]
 fn test_create() {