FAQ 27.18 Is dynamic_castT() a panacea?

FAQ 27.18 Is dynamic_cast<T>() a panacea?

No, like everything else, dynamic_cast<T>() can be misused.

It's a horrible design error, but some programmers (mis)use dynamic_cast<T>() in huge if / then / else blocks to determine an object's type and then take the appropriate action. This situation screams out for virtual functions and dynamic binding, not the extensibility-killing misuse of RTTI (see FAQ 27.03).

Also, watch out for performance hits due to this implementation technique. It is all too easy to think of dynamic_cast<T>() as a constant-time operation, when in fact it may take linear time and chew up CPU cycles if the inheritance hierarchies are deep or if the advice about huge if blocks has been ignored.