CODEWITHSUNDEEP
c++classfunctionmember
user1707244
user1707244

Reputation: 23

C++ making a class function member of another class function

I sincerely hope that people on here don't mind these sorts of questions. After having searched plenty of times, perhaps with the wrong search terms - nevertheless - I do not seem to be able to find ANYTHING on this. Yes, I have looked through cplusplus' documentation, yet I still could not find out the answer.

My question is simple, how do I make it so that a function can only be called via another function?

Here's an example

class someclas{
public:
void screen():
void setsomevariable (int somevariable){}
}clas;

And when I call the function, setsomevariable(), it should only be able to be used after having called the screen function. As such:

clas.screen().setsomevariable(..);

Again, how do I make this function a member of screen() alone?

Upvotes: 1

Views: 333

Answers (2)

Karoly Horvath
Karoly Horvath

Reputation: 96266

This does match your requirements, but doesn't necessarily meet your needs. Would like to help more but you're stubbornly refusing to give details...

class Screen {
    public:
    void setsomevariable (int somevariable) {}
};

class someclas {
    Screen s;
    public:
    Screen& screen() { return s; }
} clas;

Upvotes: 1

tomahh
tomahh

Reputation: 13661

A member function belongs to a class. You can't make a function a member of another.

You could keep a boolean in your class, and throw an exception if screen wasnt called before. But it's an ugly solution..

class someclas{
public:
  someclas & screen() { // returns a reference to your class to enable the clas.screen().setsomevariable() syntax
    screenCalled = true;
    return *this;
  }
  void setsomevariable (int somevariable){
    if (!screenCalled) {
      throw std::exception();
    }
    // some code
    screenCalled = false;
  }
  bool screenCalled;
}clas;

Upvotes: 0

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