scope error message - c++

Question

Hey guys, just learning about composition of classes and ran into this error.
Gradebook.h
#ifndef GRADEBOOK_h
#define GRADEBOOK_h
#include "StudentRec.h"
#include <iostream>
#include <string>
class GradeBook
{
public:
GradeBook();
GradeBook(string initLastName, int studGrades);
void AddStudent(string initLastName, int studGrades);
void ShowStudents();
void UserInterface();
private:
static const int numStudents=20;
StudentRec student[numStudents];
static int studentCounter;
static int gradeCounter;
};
#endif
Gradebook.cpp
#include "Gradebook.h"
#include "StudentRec.h"
#include <iostream>
#include <string>
using namespace std;
GradeBook::GradeBook()
{}
GradeBook::GradeBook(string initLastName, int studGrades)
{}
void GradeBook::AddStudent(string initLastName, int studGrades)
{
gradeCounter++; //Increments variable responsible for tracking # of grades per student
StudentRec newStudent(initLastName, studGrades); //creates new student object
student[studentCounter]=newStudent; //Assigns new student object to array
studentCounter++; //Increments variable responsible for tracking # of students
}
void GradeBook::ShowStudents()
{
for(int i=0;i<studentCounter; i++){ //Displays information for each student instance
cout<<student[i].GetLastName()<<' ';
for(int j=0; j<gradeCounter; j++)
cout<<student[i].GetGrades(j)<<' ';
cout<<endl;
}
}
void GradeBook::UserInterface()
{
char choice=' ';
string studLastName;
int studGrade;
cout<<"Welcome to GradeBook, this program stores students"
<<" grades by last name. To ADD a student press the 'A'"
<<" key. To LIST all students, press the 'L' key. To "
<<" QUIT, press the 'Q' key."<<endl<<endl;
cin>>choice;
choice=toupper(choice);
while(choice!='Q')
{
if(choice='A'){
cout<<"To add a student, please enter their last name"
<<" followed by a space and a non-negative grade"
<<" Ex. McClure 96";
cin>>studLastName>>studGrade;
AddStudent(studLastName, studGrade);
}
else if(choice='L'){
cout<<"This is a list of all students in GradeBook"
<<endl<<endl;
ShowStudents(); //Displays all StudentRec objects
}
else if(choice!='Q')
cout<<"Please enter another letter"<<endl;
cout<<"To ADD a student press the 'A' key. To LIST all students, press the 'L' key. To "
<<" QUIT, press the 'Q' key."<<endl<<endl;
}
}
Main.cpp
#include <iostream>
#include <string>
#include "StudentRec.h"
#include "Gradebook.h"
using namespace std;
int main()
{
GradeBook gradeBook;
UserInterface();
return 0;
}
StudentRec.cpp
#include <iostream>
#include <string>
#include "StudentRec.h"
using namespace std;
StudentRec::StudentRec()
{
lastName=" ";
for(int i=0;i<numGrades; i++)
grades[i]=0;
}
StudentRec::StudentRec(string initLastName, int studGrade)
{
static int gradeCounter=0;
lastName=initLastName;
grades[gradeCounter]=studGrade;
}
string StudentRec::GetLastName()
{
return lastName;
}
int StudentRec::GetGrades(int gradeNum)
{
return grades[gradeNum];
}
void StudentRec::AddGrades(int studGrade)
{
gradeCounter++;
if(gradeCounter<=numGrades)
grades[gradeCounter]=studGrade;
else
cout<<"Too many grades for this student";
}
StudentRec.h
#ifndef STUDENTREC_h
#define STUDENTREC_h
#include <iostream>
#include <string>
using namespace std;
class StudentRec
{
public:
StudentRec();
StudentRec(string initLastName, int studGrade);
string GetLastName();
int GetGrades(int gradeNum);
void AddGrades(int studGrade);
private:
static const int numGrades=10;
static int gradeCounter;
string lastName;
int grades[numGrades];
};
#endif
In the Main.cpp file, I get an error I can't find the solution for. It reads
error: "UserInterface" was not declared in this scope. I got this error while compiling in XCode
I got error C3861: 'UserInterface': identifier not found
Obviously i've tried it in two IDEs, I also have the StudentRec.cpp and .h, but not sure you need them. Thanks in advance for the help

Answer 1

It appears that UserInterface() is actually a member function of GradeBook, correct?
If so, you need to add a declaration for the member function in the GradeBook class declaration:
class GradeBook
{
public:
GradeBook();
GradeBook(string initLastName, int studGrades);
void AddStudent(string initLastName, int studGrades);
void ShowStudents();
void UserInterface(); // Added
// ...
private:
// ...
};
This way, the compiler will "know" that the UserInterface() function exists as a member function. You then provided the definition in void GradeBook::UserInterface() in your .cpp file.
Then you need to call it on a GradeBook instance, like the gradeBook variable in your main() function:
int main()
{
GradeBook gradeBook;
// This calls the member function UserInterface() on the gradeBook variable.
gradeBook.UserInterface();
// This calls the global UserInterface(), which doesn't exist.
// UserInterface();
return 0;
}

Answer 2

UserInterface() is a method of GradeBook. The call probably needs to be:
gradeBook.UserInterface();