Added virtual destructors

Author: Christian Howe

Diff for: animal.c

@@ -10,6 +10,7 @@ int animal_new(animal_t* self, const char* type, const char* name) {
   }
 
   self->vtable.speak = NULL;
+  self->vtable.delete = NULL;
 
   self->name = malloc(strlen(name)+1);
   strcpy(self->name, name);
@@ -24,6 +25,10 @@ int animal_new(animal_t* self, const char* type, const char* name) {
 }
 
 int animal_delete(animal_t* self) {
+  if (self->vtable.delete != NULL) {
+    return self->vtable.delete(self);
+  }
+
   if (self->name != NULL) {
     free(self->name);
     self->name = NULL;

Diff for: animal.h

@@ -10,6 +10,7 @@
 typedef struct {
   struct {
     void (*speak)(void* self);
+    int (*delete)(void* self);
   } vtable;
 
   void* private;

Diff for: dog.c

@@ -10,6 +10,12 @@ void dog_speak (void* _self) {
   printf("'woof!' says the %s %s dog!\n", Dog.getSize(self), Dog.getFurColor(self));
 }
 
+int dog_parent_delete(void* _self) {
+  dog_t* self = _self;
+  self->super.vtable.delete = NULL;
+  Dog.delete(self);
+}
+
 int dog_new (dog_t* self, const char* name, const char* furColor, const char* size) {
   if (furColor == NULL || size == NULL) {
     return ERROR_VAL;
@@ -18,6 +24,7 @@ int dog_new (dog_t* self, const char* name, const char* furColor, const char* si
   Animal.new(&(self->super), "dog", name);
 
   self->super.vtable.speak = &dog_speak;
+  self->super.vtable.delete = &dog_parent_delete;
 
   self->private = malloc(sizeof(dog_p));
   dog_p* private = self->private;

Diff for: main.c

@@ -17,7 +17,7 @@ int main (int argc, char* argv[]) {
 
   Animal.delete(&cat);
 
-  Dog.delete(dog);
+  Animal.delete((animal_t*)dog);
   free(dog);
 
   return 0;