Thread: Problems w.r.t Virtual Base Class (inheritance)

  1. #1
    Registered User
    Join Date
    Apr 2002
    Posts
    1

    Question Problems w.r.t Virtual Base Class (inheritance)

    This is a problem I have encountered when inheriting a virtual base class without having default arguments.

    X (base class)

    Y( virtual base class, derived from X)

    A(derived class, derived from Y)


    I have made provision in class Y to pass values to the constructor of X but when I try to create an object of class A, it get the following error message

    Error Message:
    ---------------------
    Compiling...
    Cpp2.cpp
    D:\My Projects\SampleProj\Cpp2.cpp(31) : error C2512: 'X::X' : no appropriate default constructor available
    Error executing cl.exe.
    --------------------



    Code:
    ----------------------------
    #include <iostream>
    using namespace std;

    class X
    {
    int i;

    public:
    X(int p){ i = p; }
    void show() { cout << "show:the value of i is " << i << endl; }
    };


    class Y : virtual public X
    {

    public:
    Y(int y) : X(y)
    {
    cout << "In y" << endl;
    }
    };

    class A: public Y
    {

    public:

    A(): Y(10)
    {
    cout << "In A" << endl;
    }
    };


    int main()
    {
    A a1;
    a1.show();
    return 0;
    }

    ------------------------------

    Is there any specific reason for this behaviour. If you can answer this question, would be of great help.

    Regards
    Pankajdynamic

  2. #2
    Unregistered
    Guest
    Try adding a constructor to X:
    X::X(void)
    { }

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