How can I validate a C++ object's state upon access without duplication - c++

Question

I have a C++ object running in a separate thread, with its state being updated in an asynchronous manner. The code resembles the following:
class Controller : public Listener {
public:
// Controller methods, to be called by the user from the main thread
// My problem is that I am obliged to duplicate the call to validateState() in all methods
void doAction1() {
validateState(); // explicit call to validate state
}
void doAction2() {
validateState(); // explicit call to validate state duplicated here and in every doActionX() method.
}
...
private:
// Override Listener virtual methods(which are used as callbacks), called in an async manner
void onXYZ() override;
void onError(std::string) override { /* update m_error */ }
...
// validate that no error has occurred
void validateState() {
if(m_error) throw m_error;
}
private:
Error m_error; // updated
};
I thought of a solution, to overload operator-> and call validateState() once inside, and thus removing the duplicated calls. However, the problem is that the user must do controller->doAction1() and be prohibited from doing controller.doAction1().
I can also think of other semantic issues with this approach:
One would expect overloading operator-> would be done for memory management issues (such as having a custom allocator), and not just any random operation.
the lack of symmetry between -> and .
Is duplicating the call for validateState() on newly added methods OK here? The intent being to avoid over-engineered designs.
What would be a plausible approach/design here?

Answer 1

It's perfectly fine for all the public functions of a class to call the same private function. Your function is just making sure the implicit this parameter is valid, which is the same as any other parameter validation
void Controller::doAction1(Arg1 arg1)
{
// ensure preconditions hold
validateState();
validateArg1(arg1);
// "real" code
}
void Controller::doAction2(Arg2 arg2, Arg3 arg3)
{
// ensure preconditions hold
validateState();
validateArg2(arg2);
validateArg3(arg3);
// "real" code
}