Taking user input from a created class - c++

Question

I'm new to programming, I have been reading Sams Teach Yourself C++ in 24 hours. I just started learning classes and am confused on how to allow user input on private data. I created the following class that returns the area of a Trapezoid. Any suggestions would be greatly appreciated.
class Trapezoid
{
//assigns a number to a variable
private:
int a = 20;
int b = 25;
int height = 30;
int area;
public:
int getArea();
};
int Trapezoid::getArea()
{
// calculates the area and returns it.
area = (a + b) / 2 + height;
return area;
}
#include "AreaTrapezoid.hpp"
#include <iostream>
int main()
{
// accesses area inside the Trapeziod class.
Trapezoid areaT;
areaT.getArea();
// displays the area result
std::cout << "The area of a Trapezoid: " << areaT.getArea() << std::endl;
std::cout << system("pause");
return 0;
}

Answer 1

You need to read the user's input, and then expose public access to assign new values to the class's private members. For example:
class Trapezoid
{
//assigns a number to a variable
private:
int a = 20;
int b = 25;
int height = 30;
public:
int getArea();
void setA(int value);
void setB(int value);
void setHeight(int value);
};
int Trapezoid::getArea()
{
// calculates the area and returns it.
return (a + b) / 2 + height;
}
void Trapezoid::setA(int value)
{
a = value;
}
void Trapezoid::setB(int value);
{
b = value;
}
void Trapezoid::setHeight(int value)
{
height = value;
}
#include <iostream>
#include <limits>
#include <cstdlib>
#include "AreaTrapezoid.hpp"
int main()
{
Trapezoid areaT;
int value;
// get the user's input and apply it to the Trapeziod.
std::cout << "Enter A: ";
std::cin >> value;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
areaT.setA(value);
std::cout << "Enter B: ";
std::cin >> value;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
areaT.setB(value);
std::cout << "Enter Height: ";
std::cin >> value;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
areaT.setHeight(value);
// displays the area result
std::cout << "The area of the Trapezoid: " << areaT.getArea() << std::endl;
std::system("pause");
return 0;
}
Alternatively, use a constructor instead:
class Trapezoid
{
//assigns a number to a variable
private:
int a;
int b;
int height;
public:
Trapezoid(int a, int b, int height);
int getArea();
};
Trapezoid::Trapezoid(int a, int b, int height)
: a(a), b(b), height(height)
{
}
int Trapezoid::getArea()
{
// calculates the area and returns it.
return (a + b) / 2 + height;
}
#include <iostream>
#include <limits>
#include <cstdlib>
#include "AreaTrapezoid.hpp"
int main()
{
int a, b, h;
// get the user's input and apply it to the Trapeziod.
std::cout << "Enter A: ";
std::cin >> a;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
std::cout << "Enter B: ";
std::cin >> b;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
areaT.setB(value);
std::cout << "Enter Height: ";
std::cin >> h;
std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
// displays the area result
Trapezoid areaT(a, b, h);
std::cout << "The area of the Trapezoid: " << areaT.getArea() << std::endl;
std::system("pause");
return 0;
}