Sealed classes

Sealed classes

• Unbroken73

  Than make it protected.
  
  If the constructor is protected or private no onw can create an object of this instance. Except a static function or you derive from it.
  
  class A
  {
     A() {}
  };
  
  void foo()
  {
     A instanceOfA;
  }
  
  Gives an error as expected!
  
  

• Justin-M

  Hi,
  
  Thanks. If we implement the class with private constructor, we can't inherit. But, it is giving Runtime error.Instead of that, i want to validate it in compilation time. is there any way
  
  kedar.
  

• Pete Cotton

  You cannot protect a class against derivation. But you can protect the creation of the class, this is the idea.
  If the class can only be constructed by a factory (static function inside) nobody can derive it.
  
  class A
  {
  private:
     A() {}
  public:
     static A* Construct()   
     {
        return new A();
     }
  }
  
  void Foo()
  {
     A *pA = A::Construct();
     delete pA;
  }
  
  Nobody can create a derivied class of A!
  You can not protect anybody to do this:
  class B : public A
  {
  };
  
  But nobody can create the class B!
  The .NET languages have a keyword sealed. This is not available in native C++.
  HTH
  
  

• anton pakhomov

  Hi martin,
  
  It doesn't make any difference. I want to control the user from extending my class at the compilation time.
  
  thanks,
  kedar
  

• er824

  If you make all constructors private, then nothing can inherit from your class.  To still allow creation of objects, you need to add static methods that return instances of your class.
  
  
  
• Sealed classes