Undefined symbols building in C++ on macOS - c++

Question

While implementing class member functions in.cpp file on macOS 10.15, displaying an error:
clang: Undefined symbols for architecture x86_64:error:
"Circle::Area()", referenced from:
_main in main-4cfa92.o
"Circle::Circle(double)", referenced from:
_main in main-4cfa92.o
linker command failed with exit code 1 (use -v to see invocation)
To verrify this case, I found an example on the website to try, and it worked fine when I copied the function definitions from Circle.cpp file into Circle.h file, But when the function declaration is in Circle.h and function definition is in Circle.cpp files, respectively, an error occurs
//Circle.h
#ifndef CIRCLE_H
#define CIRCLE_H
class Circle
{
private:
double r;//radius
public:
Circle();//constructor
Circle(double R);//The constructor
double Area();//computing area
};
#endif
//Circle.cpp
#include "Circle.h"
Circle::Circle(){
this->r=5.0;
}
Circle::Circle(double R){
this->r=R;
}
double Circle::Area(){
return 3.14*r*r;
}
//main.cpp
#include <iostream>
#include "Circle.h"
using namespace std;
int main(){
Circle c(3);
cout<<"Area="<<c.Area()<<endl;
return 0;
}
Error message:
Undefined symbols for architecture x86_64:
"Circle::Area()", referenced from:
_main in main-4cfa92.o
"Circle::Circle(double)", referenced from:
_main in main-4cfa92.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

Looks like you have not included Circle.cpp in the compilation step. Make sure you include both main.cpp and Circle.cpp