c++ - Return value from Derived class to Base class -

i have value in derived class want return using function base class, possible? or have have variable declared in base class so?

would call function in derived class?

class base {     public:         int getnum() const { return number; } };  class derived : public base {     private:         int n = 50; }; 

i have value in derived class want return using function base class, possible?

yes, can use reference passed base classes constructor so:

class base {     public:         base(int& number_) : number(number_) {}          int getnum() const { return number; }     private:         int& number; };  class derived : public base {     public:         derived() : base(n) {}     private:         int n = 50; }; 

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another way (without using virtual getnum() const;) using templated base class (aka static polymorphism):

template <typename d> class base {     public:         int getnum() const { return static_cast<d*>(this)->getnum(); } };  class derived : public base<derived> {     public:         derived() {}         int getnum() const { return n; }     private:         int n = 50; };