How Can Derived Classes Leverage Base Class Constructors and Assignment Operators?

Using Base Class Constructors and Assignment Operator in Derived Classes

In C , inheritance allows derived classes to inherit certain features of their base classes. However, if a derived class requires the same set of constructors and assignment operators as its base class, it may be necessary to rewrite these functions in the derived class. This can be a tedious task, especially for assignment operators that require access to private member variables.

Fortunately, there is an alternative solution. Derived classes can explicitly call base class constructors and assignment operators. This technique allows them to utilize the existing implementation without having to rewrite it.

Consider the following code example:

<code class="cpp">class Base {
public:
    Base();
    Base(const string& s);
    Base(const Base& b) { (*this) = b; }
    Base& operator=(const Base & b);

private:
    // ... (private member variables and functions)
};

class Derived : public Base {
public:
    // Override the "foo" function without modifying other aspects of the base class
    virtual void foo() override;
};</code>

In this example, Derived inherits the constructors and assignment operator of Base. It does not need to define these functions explicitly. Instead, when constructing a Derived object or assigning a Base object to a Derived object, the compiler automatically calls the appropriate base class constructor or assignment operator.

The same strategy can be used for assignment operators:

<code class="cpp">class Base {
public:
    // ... (private member variables and functions)
    Base(const Base& b) { /* ... */ }
    Base& operator=(const Base& b) { /* ... */ }
};

class Derived : public Base {
public:
    int additional_;

    // Call the base assignment operator within the derived operator
    Derived& operator=(const Derived& d) {
        Base::operator=(d);
        additional_ = d.additional_;
        return *this;
    }
};</code>

This technique allows derived classes to fully utilize the functionality of their base classes while only overriding or adding necessary behaviors. It simplifies inheritance by eliminating the need to rewrite complex base class constructors or assignment operators.

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