Protect against an edge case of garbage collection.

beeware · Oct 30, 2023 · ff64a99 · ff64a99
1 parent 1583545
commit ff64a99
Show file tree

Hide file tree

Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/cocoa/src/toga_cocoa/constraints.py b/cocoa/src/toga_cocoa/constraints.py
@@ -34,10 +34,15 @@ def __del__(self):  # pragma: nocover
     def _remove_constraints(self):
         if self.container:
             # print(f"Remove constraints for {self.widget} in {self.container}")
-            self.container.native.removeConstraint(self.width_constraint)
-            self.container.native.removeConstraint(self.height_constraint)
-            self.container.native.removeConstraint(self.left_constraint)
-            self.container.native.removeConstraint(self.top_constraint)
+            # Due to the unpredictability of garbage collection, it's possible for
+            # the native object of the window's container to be deleted on the ObjC
+            # side before the constraints for the window have been removed. Protect
+            # against this possibility.
+            if self.container.native:
+                self.container.native.removeConstraint(self.width_constraint)
+                self.container.native.removeConstraint(self.height_constraint)
+                self.container.native.removeConstraint(self.left_constraint)
+                self.container.native.removeConstraint(self.top_constraint)
 
             self.width_constraint.release()
             self.height_constraint.release()

diff --git a/cocoa/src/toga_cocoa/container.py b/cocoa/src/toga_cocoa/container.py
@@ -84,6 +84,7 @@ def __init__(
     def __del__(self):
         self._min_height_constraint.release()
         self._min_width_constraint.release()
+        self.native = None
 
     @property
     def content(self):