C++ Non-Static Member Functions Non-static Member Functions


Example

A class or struct can have member functions as well as member variables. These functions have syntax mostly similar to standalone functions, and can be defined either inside or outside the class definition; if defined outside the class definition, the function's name is prefixed with the class' name and the scope (::) operator.

class CL {
  public:
    void  definedInside() {}
    void definedOutside();
};
void CL::definedOutside() {}

These functions are called on an instance (or reference to an instance) of the class with the dot (.) operator, or a pointer to an instance with the arrow (->) operator, and each call is tied to the instance the function was called on; when a member function is called on an instance, it has access to all of that instance's fields (through the this pointer), but can only access other instances' fields if those instances are supplied as parameters.

struct ST {
    ST(const std::string& ss = "Wolf", int ii = 359) : s(ss), i(ii) { }

    int get_i() const { return i; }
    bool compare_i(const ST& other) const { return (i == other.i); }

  private:
    std::string s;
    int i;
};
ST st1;
ST st2("Species", 8472);

int  i = st1.get_i(); // Can access st1.i, but not st2.i.
bool b = st1.compare_i(st2); // Can access st1 & st2.

These functions are allowed to access member variables and/or other member functions, regardless of either the variable or function's access modifiers. They can also be written out-of-order, accessing member variables and/or calling member functions declared before them, as the entire class definition must be parsed before the compiler can begin to compile a class.

class Access {
  public:
    Access(int i_ = 8088, int j_ = 8086, int k_ = 6502) : i(i_), j(j_), k(k_) {}

    int i;
    int get_k() const { return k; }
    bool private_no_more() const { return i_be_private(); }
  protected:
    int j;
    int get_i() const { return i; }
  private:
    int k;
    int get_j() const { return j; }
    bool i_be_private() const { return ((i > j) && (k < j)); }
};