Composition syntax in C++ - c++

Question

I am in the middle of getting my feet wet with the use of composition & classes in C++. A code snippet I came across implements composition in the following manner:
#include<iostream>
using namespace std;
class Engine {
public:
int power;
};
class Car {
public:
Engine e;
string company;
string color;
void show_details() {
cout << "Compnay is: " << company << endl;
cout << "Color is: " << color << endl;
cout << "Engine horse power is: " << e.power << endl;
}
};
int main() {
Car c;
c.e.power = 500;
c.company = "hyundai";
c.color = "black";
c.show_details();
return 0;
}
This compiles fine, and runs. One thing I do not like about this implementation is the actual location of the function "void show_details", which I would prefer to place outside.
However, if I naively try to do the following:
#include<iostream>
using namespace std;
class Engine {
public:
int power;
};
class Car {
public:
//Engine e;
string company;
string color;
void show_details();
//void show_details() {
// cout << "Compnay is: " << company << endl;
// cout << "Color is: " << color << endl;
// cout << "Engine horse power is: " << e.power << endl;
//}
};
void Car::show_details(){
cout << "Compnay is: " << company << endl;
cout << "Color is: " << color << endl;
cout << "Engine horse power is: " << e.power << endl;
}
int main() {
Car c;
c.e.power = 500;
c.company = "hyundai";
c.color = "black";
c.show_details();
return 0;
}
g++ returns the following errors:
comp3.cpp: In member function ‘void Car::show_details()’:
comp3.cpp:22:44: error: ‘e’ was not declared in this scope
cout << "Engine horse power is: " << e.power << endl;
^
comp3.cpp: In function ‘int main()’:
comp3.cpp:26:9: error: ‘class Car’ has no member named ‘e’
c.e.power = 500;
I am clearly confused regarding issues of scoping, but I am not sure as to what the missing piece is.
Thanks for any & all help!!!

Answer 1

In the second example you commented out e.
//Engine e;