Solved

Is This Valid C++?

Posted on 1998-06-29
1
212 Views
Last Modified: 2010-04-01
Environment Visual C++ 5.0.

This compiles and appears to run OK but I was wondering whether it is valid (or good) C++. And if not is there a better way to do it?

class COther
{

protected:
      int x;
      int y;

public:
      COther();
      ~COther();
      virtual void set_values(int px,int py)
      {
            x = px;
            y = py;
      }
};

class A
{

protected:
      COther* other_class;

public:
      virtual void do_work()
      {
            other_class = new COther;
            other_class->set_values(2,4);
      }
};

class CNewOther : public COther
{
      int z;

public:
      CNewOther();
      ~CNewOther();
      virtual void set_values(int px,int py)
      {
            y = px;
            x = py;
            z = y*x;
      }
};

class B : public A
{
      virtual void do_work()
      {
            other_class = new CNewOther;
            other_class->set_values(2,4);
      }
};

This is a simple example of the actual code that has been written. It just struck me that this might potentially cause problems because the declared pointer is not the same as the instantiated type for the other_class object.

Any comments?
0
Comment
Question by:sdj
1 Comment
 
LVL 1

Accepted Solution

by:
cmw earned 50 total points
ID: 1166775
Yes, this is valid. It works because you declare the set_values method virtual. So code is inserted to find out what the pointer points to, and to call the correct method. Leave out the virtual, and the compiler will assume that type of the pointer is allways correct, and try to call COther::set_values(). The virtual needs only to be specified at the root level, but I prefer to mention it through the hierarchy.

As to the question if it can be done differently, well I suppose you think of all sorts of ways of doing this, but it really depends on what you are trying to achieve. In general, Objects of classes should encapsulate the behaviour for which they are responsible. You do not mention what your objective is, so this isn't as straightforward.
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When writing generic code, using template meta-programming techniques, it is sometimes useful to know if a type is convertible to another type. A good example of when this might be is if you are writing diagnostic instrumentation for code to generat…
  Included as part of the C++ Standard Template Library (STL) is a collection of generic containers. Each of these containers serves a different purpose and has different pros and cons. It is often difficult to decide which container to use and …
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

790 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question