C++ – Force a Derived Class to use the Constructor of the Base Class

cclassconstructorinheritanceoop

Is there a way to force a derived class to use the constructor of the abstract base class? It must not be a real constructor, I have an open mind about creative solutions.

class Abstract
{
private:
    int Member;
    string Text;

public:
    Abstract(int Member, string Text)
    {
        this->Member = Member; 
        this->Text = Text;
    }

    // e.g. defining virtual functions
}

For example my abstract class has some private members which every derived class should also have. And they should be defined in the constructor, even against the will of the derived class.

I am aware that constructors are not inherited. But is there a workaround to produce a similar behavior?

Best Answer

As suggested by other users, you must call the base class constructor into the initializer list of derived class constructor.

But there's another cool solution bringed up by C++11: the inherited constructors:

class Base
{
    Base(int Member, string Text) { };
};

class Derived : public Base
{
    using Base::Base; // <-- Brings to derived the Base's constructor.
};

But you must assure that your compiler can use C++11 features; and of course, study if the inherited constructor conforms to your requirements instead of using it just because it's cool.

Related Solutions

C# – Calling the base constructor in C#

Modify your constructor to the following so that it calls the base class constructor properly:

public class MyExceptionClass : Exception
{
    public MyExceptionClass(string message, string extrainfo) : base(message)
    {
        //other stuff here
    }
}

Note that a constructor is not something that you can call anytime within a method. That's the reason you're getting errors in your call in the constructor body.

C++ – When should you use a class vs a struct in C++

The differences between a class and a struct in C++ is:

struct members and base classes/structs are public by default.
class members and base classes/struts are private by default.

Both classes and structs can have a mixture of public, protected and private members, can use inheritance and can have member functions.

I would recommend you:

use struct for plain-old-data structures without any class-like features;
use class when you make use of features such as private or protected members, non-default constructors and operators, etc.

Best Answer

Related Solutions

C# – Calling the base constructor in C#

C++ – When should you use a class vs a struct in C++

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