CODEWITHSUNDEEP
c++private
jason
jason

Reputation: 7164

Private element error

Class 1:

class Class1{
public:
    Class1(Class2 * a, int b );
    ~Class1();
    friend ostream& operator<< (ostream& x, const Class1& c1);

private:
    int b;
    Class2 * a;
};

ostream& operator<< (ostream& x, const Class1& c1)
{
    stream<<"("<<c1.a->label<<","<<c1.b<<")"<<endl;
    return x;
}

Class2 (In another file):

class Class2
{
public : 
   Class2 (string label);
   ~Class2();
  string getLabel()
  {
     return label; 
  }

private:
    string label;
    vector<Class1 *> c1vector;
};

Question:

I'm trying to print the label and b of an edge, but it says the label is private. Can you tell me what I'm doing wrong? Thanks.

Upvotes: 0

Views: 57

Answers (4)

JBL
JBL

Reputation: 12907

Well, you are trying to access a private member of Class2 directly, and the private property is actually what prevents you from doing this. (And the fact that you qualified operator<< friend in Class1 doesn't change anything, label is a private member of Class2).

Either make the member public (not recommended) or provide a public member function that returns the value of this member.

Upvotes: 1

taocp
taocp

Reputation: 23624

One issue is that: label is private in Class2, you cannot directly access it inside Class1 via an instance of Class2, which is a in this case. You may need to provide getters inside Class2.

 class Class2
 {
  public : 
      string getLable()
      {
         return label; 
      }
  private:
     string label;
};//^^other members skipped for clearance purpose

Upvotes: 1

Mark B
Mark B

Reputation: 96233

label is private within Class2 so it cannot be access through Class or your operator<< insertion function. The simplest solution is to provide a public const get_label function in Class2 to access the label string.

A more in depth approach is to give Class2 its own print mechanism (either through a print/display/show function, or with its own operator<< that can be used to show the label.

Upvotes: 1

Hola Soy Edu Feliz Navidad
Hola Soy Edu Feliz Navidad

Reputation: 7072

You have to write in Class2 friend ostream& operator<< (ostream& x, const Class1& c1);, because only Class 1 is its friends but label if a private attibute of class2

Upvotes: 1

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