Inheritence and usage of dynamic_cast
- by Mewzer
Hello,
Suppose I have 3 classes as follows (as this is an example, it will not compile!):
class Base
{
public:
Base(){}
virtual ~Base(){}
virtual void DoSomething() = 0;
virtual void DoSomethingElse() = 0;
};
class Derived1
{
public:
Derived1(){}
virtual ~Derived1(){}
virtual void DoSomething(){ ... }
virtual void DoSomethingElse(){ ... }
virtual void SpecialD1DoSomething{ ... }
};
class Derived2
{
public:
Derived2(){}
virtual ~Derived2(){}
virtual void DoSomething(){ ... }
virtual void DoSomethingElse(){ ... }
virtual void SpecialD2DoSomething{ ... }
};
I want to create an instance of Derived1 or Derived2 depending on some setting that is not available until run-time.
As I cannot determine the derived type until run-time, then do you think the following is bad practice?...
class X
{
public:
....
void GetConfigurationValue()
{
....
// Get configuration setting, I need a "Derived1"
b = new Derived1();
// Now I want to call the special DoSomething for Derived1
(dynamic_cast<Derived1*>(b))->SpecialD1DoSomething();
}
private:
Base* b;
};
I have generally read that usage of dynamic_cast is bad, but as I said, I don't know
which type to create until run-time. Please help!
