purpose of pure virtual function

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C#

I know about the definition of pure virtual function but what is purpose of pure virtual function

Posted 6-Sep-11 2:56am

umairshoaib

Updated 6-Sep-11 2:58am

Reiss

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Reiss 6-Sep-11 8:59am

Please don't use all caps - it is considered shouting.

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#realJSOP · Accepted Answer · 2011-09-06T03:01:00

Solution 1

A pure virtual function makes the class an abstract class, which itself cannot be instantiated. This means that to use the class, you have to inherit from it, and you MUST override all pure virtual functions defined in the abstract class.

Posted 6-Sep-11 3:01am

#realJSOP

v2

Comments

CPallini 6-Sep-11 9:04am

My 5.

Uday P.Singh 6-Sep-11 9:07am

correct my 5!

Espen Harlinn 6-Sep-11 18:32pm

Agree :)

Philippe Mori 6-Sep-11 20:19pm

A pure virtual function (and an abstract class) has a similarity with functions inside an interface because they need to be implemented by derived classes. The main difference is the intended usage (implementation of the base class vs public interface to a class).

Reiss · Accepted Answer · 2011-09-06T03:06:00

Further to John's answer this code snippet should show you what is going on.

C#

namespace Dummy
{
    public abstract class PureVirtualFunction
    {
        public abstract void Method();
    }

    public abstract class VirtualFunction
    {
        public virtual void Method()
        {
            // do something
        }
    }

    public class PureVirtualFunction_Inherited : PureVirtualFunction
    {
        public override void Method()
        {
            // must provide own implentation
        }
    }

    public class VirtualFunction_Inherited_Base : VirtualFunction
    {
        // uses base method implementation
    }

    public class VirtualFunction_Inherited_Overrides : VirtualFunction
    {
        public override void Method()
        {
            // my implementation
        }
    }
}