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    <p>If you are using the 'I' prefix to mean "interface" as it would mean in Java, which would be done with abstract bases in C++, then your first option will fail to work....so that one's out. I have used it for some things though.</p> <p>Don't do 'd', it will pollute your hierarchy. Keep your interfaces clean, you'll be glad you did. Thus a Vehicle class doesn't have a pedal() function because only some vehicles can pedal. If a client needs the pedal() function then it really does need to know about those classes that can.</p> <p>Stay way clear of 'e' for the same reason as 'd' PLUS that it violates the Liskov Substitution Principle. If a client needs to check that a class responds to pedal() before calling it so that it doesn't explode then the best way to do that is to attempt casting to an object that has that function. 'f' is just the same thing with the check.</p> <p>'c' is superfluous. If you have your hierarchy set up the way it should be then casting to ICanDoX is sufficient to check if x can do X().</p> <p>Thus 'b' becomes your answer from the options given. However, as Gladfelter demonstrates, there are options you haven't considered in your post.</p> <p>Edit note: I did not notice that 'c' used a static_cast rather than dynamic. As I mention in an answer about that, the dynamic_cast version is cleaner and should be preferred unless specific situations dictate otherwise. It's similar to the following options in that it pollutes the base interface.</p> <p>Edit 2: I should note that in regard to 'a', I have used it but I don't use types statically like you have in your post. Any time I've used typeid to split flow based on type it has always been based on something that is registered during runtime. For example, opening the correct dialog to edit some object of unknown type: the dialog governors are registered with a factory based on the type they edit. This keeps me from having to change any of the flow control code when I add/remove/change objects. I generally wouldn't use this option under different circumstances.</p>
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    1. COwhy doesnt (a) work?
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    2. CO@pm - because if the variable is a subclass of the interface then you won't get that typeid back.
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    3. COah - i had not realized that. I assumed that it would be true if the object could be cast to that type. Once more I am expecting c++ to be ore like c# or jave
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