objects-classes, ch3: explaining the 'fix' for the statics subclass g…

…otcha

objects-classes/ch3.md

@@ -1099,7 +1099,7 @@ The `#printError()` static private function here has a `this`, but that's refere
 
 Remember: private statics are similarly not-inherited by subclasses just as private members/methods are not.
 
-#### Subclassing Gotcha
+#### Gotcha: Subclassing With Static Privates and `this`
 
 Recall that inherited methods, invoked from a subclass, have no trouble accessing (via `this.#whatever` style references) any privates from their own base class:
 
@@ -1129,7 +1129,7 @@ point.printID();
 
 That works just fine.
 
-Unfortunately, and (to me) a little unexpectedly/inconsistently, the same is not true of private statics accessed from inherited public static functions:
+Unfortunately, and (to me) quite unexpectedly/inconsistently, the same is not true of private statics accessed from inherited public static functions:
 
 ```js
 class Point2d {
@@ -1158,7 +1158,33 @@ Point3d.printError();
 
 The `printError()` static is inherited (shared via `[[Prototype]]`) from `Point2d` to `Point3d` just fine, which is why the function references are identical. Like the non-static snippet just above, you might have expected the `Point3d.printError()` static invocation to resolve via the `[[Prototype]]` chain to its original base class (`Point2d`) location, thereby letting it access the base class's `#errorMsg` static private.
 
-But it fails, as shown by the last statement in that snippet. Beware that gotcha!
+But it fails, as shown by the last statement in that snippet. The reason it fails here, but not with the previous snippet, is a convoluted brain twister. I'm not going to dig into the *why* explanation here, frankly because it boils my blood to do so.
+
+There's a *fix*, though. In the static function, instead of `this.#errorMsg`, swap that for `Point2d.#errorMsg`, and now it works:
+
+```js
+class Point2d {
+ static #errorMsg = "Out of bounds."
+ static printError() {
+ // the fixed reference vvvvvv
+ console.log(`Error: ${Point2d.#errorMsg}`);
+ }
+
+ // ..
+}
+
+class Point3d extends Point2d {
+ // ..
+}
+
+Point2d.printError();
+// Error: Out of bounds.
+
+Point3d.printError();
+// Error: Out of bounds. <-- phew, it works now!
+```
+
+If public static functions are being inherited, use the class name to access any private statics instead of using `this.` references. Beware that gotcha!
 
 ## Class Example