[Jihgfed Pumpkinhead]

I want to create a class which will manage my event flags; I was thinking the best way to store the data would be to use a std::vector . At first, I thought I'd implement it with inheritance, but then I decided it would be simpler and more sensible just to use composition. However, I still would like to know if my inheritance code would make sense, for future reference.

[Ninkazu]

Heh, I wouldn't use inheritance, I'd just have a member variable be a vector. If you're going to use inheritance, it should be because you want to rewrite some of vector's code, which is polymorphism. Since you don't have the original source to it anyway, it's kinda pointless.

[Jihgfed Pumpkinhead]

Yes, I said I'd use composition, i.e., use of a member variable. My actual code looks something like this:

[DrV]

Hmm... in Perl, a bit vector is just a string of integers that can be modified bit by bit, just like you had done something like

[Guest]

No! You should not inherit for multiple reasons

1: inhertiance implies an "Is-A" relationship

what this means is that if you would inherit your event list
from vectro everything that's valid on such should
be valid on the EventList and I figoure this is hardly the case

2: STL classes aren't designed to be inherited from
Any class designed to inherit from have both of theese:
a) a virtual destructor
b) at least 1 virtual memberfunction

STL classes have none of theese making them ill suited for
inhertiance opening the door for "undefined behaviour"

so just don't.

You should always use the weakest relationship between classes
possible, and apart from friends inhertiance is as strong as they
come.

[DrunkenCoder]

And that was me...
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[Jihgfed Pumpkinhead]

Gee, some people sure are scary when their OOP is threatened. Heh heh.

Anyway, like I said, I decided to use composition instead of inheritance. I thought of inheritance first, but then I realized I only wanted a couple functions, and was scared of opening up the whole interface (since EventList "Has A" vector of bools, but "Is Not A" vector of bools itself).

But you're right, I never should have considered inheriting from an STL member in the first place.

And, um, what's a virtual constructor? That sounds profoundly mad.

And DrV, thanks for actually reading my post, unlike some people who skip straight to the code block (heh). Yes, I think that's exactly the idea behind a bit_vector, although I'm talking about an STL version (which I've just found: http://www.sgi.com/tech/stl/bit_vector.html, so no one worry about it anymore).

[DrunkenCoder]

I never said virtual constructor there's no such thing (altough it's often usefull to mimic that behavoir) I said virtual destructor

not having a virtual destructor in any class you inherit from
is a really bad thing the best thing that can happen is a memory
leak... the worst... well it's undefined behavoir so mostly anything.

the problem arise when you try do delete a derived object
through a base class pointer, the wrong destructor gets called
and I think we all can agree that's a really bad thing

but on the topic of virtualizing constructors that is often achived through
an abstract base and something called a factory
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If there's life after death there is no death, if there's no death we never live. | ENTP

[Rainer Deyke]

[Jihgfed Pumpkinhead]

Sorry; I always seem to say constructor when I mean destructor.

Oh, I see. I'd thought that the correct destructor would automatically get called, even if you're dealing with a pointer to a base class. That's scary; I'll go fix that now, thanks.

Now, in the following:

[grenideer]

No. There's no downside to making a destructor virtual (except overhead). Making a destructor (or any class function) virtual makes it 'smart' (dynamic). That means at RUN-TIME the program decides which destructor (or other function) to call. If you are using a pointer to a base class that is pointing to a child class, then although the pointer is of type *base class*, the destructor is smart and sees that it is actually pointing to a *child class* and calls that destructor instead.

Rainer, although you're right about using a non-virtual destructor being safe (actually the same thing DrunkenCoder said), it REALLY is bad style. And covering your a$$ beforehand is the best way to stay outta trouble. If later on down the line you use a base class pointer (or say, someone else on your team of coders [since we're talking in terms of game-programming]) , that'll be a very hard bug to catch.
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Diver Down

[grenideer]

Jihgfed, to answer your original question, the first line of code you were wondering about makes sense (using the push_back() function). That second line may or may not, depending on whether or not you overloaded the [] operators. Can your EventList class objects access elements with the brackets? If they can, then the line works. Although I'm assuming you're gonna do something else with that bool you caught- otherwise it's wasted.

Um, yeh, to add to Ninkazu's original reply (that the reason to use inheritance is to overload member functions) I just wanted to state the second reason to use inheritance - which is to directly access private or protected members of the base class. And I agree with everyone else (even you) that there's no reason inheritance should ever have been considered in this case.
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Diver Down

[DrunkenCoder]

[DrunkenCoder]

to nitpick on greindeers post.

Inheriting doesn't give access to private data in the base only to protected.

And as everyone seems to be in a really nitpicky mode I can also clearify that mostly when we talked about inheritance here we have ment *public* inhertiance, don't forget the more esotroic flavours of protected and even private inhertance although not common they do have uses.
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If there's life after death there is no death, if there's no death we never live. | ENTP

[Jihgfed Pumpkinhead]

Okay, thanks a lot, everybody. I have one more (hopefully, one last) question.

I'm trying to set up my operator[], but I'm having difficulty.