Re: dynamic function definition

From:
"Robbie Hatley" <bogus.address@no.spam>
Newsgroups:
comp.lang.c++
Date:
Tue, 11 Jul 2006 09:20:49 GMT
Message-ID:
<R3Ksg.118623$H71.6427@newssvr13.news.prodigy.com>
"cesco" <fd.calabrese@gmail.com> wrote:

I need to define the body of a function in the constructor of a class.
For example, the class has a member function Log (that is the public
interface of the class), but I want the body of this function to be
defined as something or as something else in the constructor of the
class:

class MyClass
{
public:
void Log(const int& id, const int& value);
private:
void LogON(const int& id, const int& value);
void LogOFF();

};

MyClass::MyClass
{
// define here whether the function "Log" will behave as LogON or
LogOFF according to a switch
}

void MyClass::LogON(const int& id, const int& value)
{
// do something like push_back
}

void MyClass::LogOFF()
{
// do nothing
}

// don't know if I need or not the following definition
void MyClass::Log(const int& id, const int& value)
{
}

Any suggestion on how to do this?


Yes. Use an interpreted language such as APL or Perl.
On-the-fly self-reprogramming programs are impossible in
a compiled language such as C++.

But you really don't need "dynamic function definition" for
what you describe. Polymorphism would work for you, I think.

Something like:

class MyLogBase // Abstract base; can't be instantiated
{
   public:
      // (contstructors, etc.)

      // Pure Virtual Function:
      virtual void Log(const int& id, const int& value) = 0;

   private:
      // etc.
};

class MyLogOn : public MyLogBase
{
   public:
      // (contstructors, etc.)

      // over-ride the pure virtual function from the base:
      void Log(const int& id, const int& value)
      {
         std::cout << "LOG ON" << std::endl;
      }
   private:
      // etc.
};

class MyLogOff : public MyLogBase
{
   public:
      // (contstructors, etc.)

      // over-ride the pure virtual function from the base:
      void Log(const int& id, const int& value)
      {
         std::cout << "LOG OFF" << std::endl;
      }
   private:
      // etc.
};

Research "polymorphism", "pure virtual function", and
"abstract base class" in a good C++ book for more info.

--
Cheers,
Robbie Hatley
East Tustin, CA, USA
lone wolf intj at pac bell dot net
(put "[usenet]" in subject to bypass spam filter)
http://home.pacbell.net/earnur/

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