Class variables: public access read-only, but private access read/write

Question

Whoopee, not working on that socket library for the moment. I'm trying to educate myself a little more in C++.

With classes, is there a way to make a variable read-only to the public, but read+write when accessed privately? e.g. something like this:

class myClass {     private:     int x; // this could be any type, hypothetically      public:     void f() {         x = 10; // this is OK     } }  int main() {     myClass temp;      // I want this, but with private: it's not allowed     cout << temp.x << endl;       // this is what I want:      // this to be allowed     temp.f(); // this sets x...      // this to be allowed     int myint = temp.x;      // this NOT to be allowed     temp.x = myint; } 

My question, condensed, is how to allow full access to x from within f() but read-only access from anywhere else, i.e. int newint = temp.x; allowed, but temp.x = 5; not allowed? like a const variable, but writable from f()...

EDIT: I forgot to mention that I plan to be returning a large vector instance, using a getX() function would only make a copy of that and it isn't really optimal. I could return a pointer to it, but that's bad practice iirc.

P.S.: Where would I post if I just want to basically show my knowledge of pointers and ask if it's complete or not? Thanks!

Answer 1

Of course you can:

class MyClass {     int x_;  public:     int x() const { return x_; } }; 

If you don't want to make a copy (for integers, there is no overhead), do the following:

class MyClass {     std::vector<double> v_;  public:     decltype(v)& v() const { return v_; } }; 

or with C++98:

class MyClass {     std::vector<double> v_;  public:     const std::vector<double>& v() const { return v_; } }; 

This does not make any copy. It returns a reference to const.