Virtual function call

Question

Here is my hierarchic of classes.

I have declare following abstract interface class, which have just one function:

class IAuthenticator
{
public:
    virtual void CreateJson() = 0;
};

After I have created on more class 'UIData' and inherits it from interface class, in this case:

class UIData : public IAuthenticator
{
protected:
    UIData() : mWindowHandle(0) 
    { /* Constructor do nothing. **/ }

private:
    integer mWindowHandle;

public:
    void CreateJson()
    {
        std::cout<<"UIData::CreateJson\n";
    }

};

I have one more class which inherits from UIData

class AuthenticateIn : public UIData
{
private:
    string mOrigin;
    string mLogoURL;
    string mUserID;

public:
    void CreateJson()
    {
        std::cout<<"AuthenticateIn::CreateJson\n";
    }
};

Question

In my main function I have write code like this.

int main()
{
    AuthenticateIn* ai = new AuthenticateIn();
    ai->CreateJson();
}

When I call CreateJson() function I see log "AuthenticateIn::CreateJson". I want to find a way to call CreateJson() and it will be called for all base classes.

I know that I can do that calling this->UIData::CreateJson() from AuthenticateIn class CreateJson function, but is there any other way to do that, some automatic way ? Thanks !!

Answer 1

is there any other way to do that, some automatic way

No, there isn't. You have to call the base class's implementation from the derived class. The compiler won't do this automatically since it doesn't know whether you actually want this.

Answer 2

You have to call the base class function in the derived class sort of like this:

void CreateJson() {
    UIData::CreateJSon();
}

etc

Answer 3

No, there is no such way. If you want to call virtual function from base class you should do this directly.

Answer 4

You may not be able to force a call to a virtual base class, but you can use indirection to simulate the behaviour.

typedef int integer;

#include <iostream>
#include <string>

using std::string;
using std::cout;
class IAuthenticator
{
public:
    virtual void CreateJson() = 0;
};

class UIData : public IAuthenticator
{
protected:
    UIData() : mWindowHandle(0)
    { /* Constructor do nothing. **/ }

private:
    integer mWindowHandle;
    virtual void CreateJsonPrivate() = 0;

public:
    void CreateJson()
    {
        CreateJsonPrivate();
        std::cout<<"UIData::CreateJson\n";
    }

};

class AuthenticateIn : public UIData
{
private:
    string mOrigin;
    string mLogoURL;
    string mUserID;

    virtual void CreateJsonPrivate()
    {
        std::cout<<"AuthenticateIn::CreateJson\n";
    }
};

int main()
{
    AuthenticateIn* ai = new AuthenticateIn();
    ai->CreateJson();
}

Output:

AuthenticateIn::CreateJson
UIData::CreateJson