Was not declared in the scope error

Question

I have a class that saves a student data. Before it will be stored, the ID will be check first if valid or not. In overloading the operator >>, I call the validate_id function. I already declared it as a friend, however upon compiling, it says 'validate_id was not declared in scope . Is it because its a static function?

#include <iostream>
#include <string>
#include <locale>  
#include <utility>
#include <algorithm>
#include <stdexcept>


typedef std::pair<std::string, std::string> Name;

class Student {

   public:
       Student(){};

       bool operator <( const Student& rhs ) const {
          return ( id_ < rhs.id_ );
        }

   friend std::ostream& operator <<(std::ostream& os, const Student& s);
   friend std::istream& operator >>(std::istream& is, Student& s);

   private:
    std::string     id_;
    Name        name_;

    static bool validate_id(const std::string& id){
        if(id.length() != 9 && id[0] != 'a')
            return false;

        for(size_t i = 1, sz = id.length(); i < sz; i++){
            if(!isdigit(id[i]))
              return false;
        }

            return true;
    }

};


std::ostream& operator <<(std::ostream& os, const Student& s){
    return os << s.id_ << " " << s.name_.first << " " << s.name_.second;
}

std::istream& operator >>(std::istream& is, Student& s){
     is >> s.id_ >> s.name_.first >> s.name_.second;

    if(!validate_id(s.id_))  // error here, says validate_id is not in scope
        throw std::invalid_argument( "invalid ID" );


    return is;
}

you're missing the scope resolution operator :: since it's a member — , Jul 12 '15 at 07:05
this is a nice review of operator overloading in c++ http://stackoverflow.com/questions/4421706/operator-overloading — , Jul 12 '15 at 07:09

score 3 · Accepted Answer · answered Jul 12 '15 at 07:02

3

validate_id is a static member of Student, so you need to use the class' scope to name it:

if(!Student::validate_id(s.id_))
    ^^^^^^^^^

answered Jul 12 '15 at 07:02

juanchopanza

223,364
34
402
480

Thanks, I forgot about that one.. my code now compiles – XDProgrammer Jul 12 '15 at 07:09

score 0 · Answer 2 · answered Jul 12 '15 at 07:21

When you are calling a static member function in c++, you have to call it with the class scope. that means here you have to use !Student::validate_id(s_id)

Meaning of a Static is that what ever you declared is goes to class scope.Not to object scope. That's why you have to call it with the class.

Paul David · Answer 3 · 2015-07-12T07:06:19.570

-1

Either declare validate_id outside of the Student class or call Student.validate_id.

edited Jul 12 '15 at 07:06

answered Jul 12 '15 at 06:59

Paul David

32
6

No need to make it public. The stream operators are `friend`s. – juanchopanza Jul 12 '15 at 07:01
I declared, a friend function inside that class, however it still says not in scope – XDProgrammer Jul 12 '15 at 07:04
1

You need to call `Student::validate_id`, not `Student.validate_id`. – PC Luddite Jul 12 '15 at 07:26

Was not declared in the scope error

3 Answers3