Scott Meyer in his book Effective C++ says dynamic_cast is used to perform safe casts down or across an inheritance hierarchy. That is, you use dynamic_cast to cast pointers or references to base class objects into pointers or references to derived or sibling base class objects in such a way that you can determine whether the casts succeeded.
Failed casts are indicated by a null pointer (when casting pointers) or an exception (when casting references).
I would like to get two code snippet showing the failed cast in the case of casting pointer and casting reference can be indicated.
For pointers, it's a simple null check:
A* a = new A();
B* b = dynamic_cast<B*>(a);
if (b == nullptr)
{
// Cast failed
}
For references, you can catch:
try {
SomeType &item = dynamic_cast<SomeType&>(obj);
}
catch(const std::bad_cast& e) {
// Cast failed
}