在 C++ 中使用 inheritance 的正方形、圆形和矩形的面积

Question

I am having an issue with my program in C++. I need to find the area of a square, circle, and rectangle. I have everything down with the circle and square but the rectangle and the shape (inheritance structure) are giving me the aforementioned issues. I have been beating my head against a wall trying to figure this out so if anyone could help me I would greatly appreciate it. My code is:

 main.cpp #include <iostream> #include "Circle.h" #include "Square.h" #include "Rectangle.h" using namespace std; int main() { double radius = 0; double length = 0; double width = 0; Square square; Circle circle; Rectangle rectangle; int option; cout << "Calculating the Area" << endl << endl; do { cout << "Pick a shape in which you would like the area of:" << endl; cout << "1: Square" << endl; cout << "2: Circle" << endl; cout << "3: Rectangle" << endl; cout << "4: Exit" << endl; cout << "Please enter your choice: "; cin >> option; switch(option) { case 1: { cout << endl; cout << "Please enter the length of one side of the square: " << endl; cin >> length; Square square(length); cout << "The area of the square is: " << square.getArea() << "\n\n"; break; } case 2: { cout << endl; cout << "Please enter the radius of the circle: "; cin >> radius; circle.setRadius(radius); cout << "The area of the circle is: " << circle.getArea() << "\n\n"; break; } case 3: { cout << endl; cout << "Please enter the length of one side of the rectangle: "; cin >> length; rectangle.setLength(length); cout << "Please enter the width of one side of the rectangle: "; cin >> width; rectangle.setWidth(width); cout << "The area of the rectangle is: " << rectangle.getArea(); } } } while (option;= 4); cout << "Bye " << endl }

shape.h

 #ifndef SHAPE_H_INCLUDED #define SHAPE_H_INCLUDED class Shape { public: double getArea(); }; #endif // SHAPE_H_INCLUDED

shape.cpp

 #include "shape.h" Shape::Shape() { area = 0; } double Shape::getArea() { return area; }

rectangle.h

 #ifndef RECTANGLE_H_INCLUDED #define RECTANGLE_H_INCLUDED #include <iostream> #include "shape.h" class Rectangle: public Shape { public: Rectangle (double length = 0, double width = 0); double getLength = 0; double getWidth = 0; void setLength(double length); void setWidth(double width); double getArea(); private: double length; double width; }; #endif // RECTANGLE_H_INCLUDED

rectangle.cpp

 #ifndef RECTANGLE_H_INCLUDED #define RECTANGLE_H_INCLUDED #include <iostream> #include "shape.h" class Rectangle: public Shape { public: Rectangle (double length = 0, double width = 0); double getLength = 0; double getWidth = 0; void setLength(double length); void setWidth(double width); double getArea(); private: double length; double width; }; #endif // RECTANGLE_H_INCLUDED

I only included the ones I am having trouble with. Seeing as how I know my other ones work and that this is a rewrite of a program I did last week. Every time I try to build it I get these two errors.

Definition of implicitly-declared 'Shape::shape()' area was not declared in this scope.

Any help would be greatly appreciated.

Answer 1

1) change your Shape class as

class Shape { public: Shape(); double getArea(); double area; };

You have not defined constructor of class and area

2) You wrote same code in Rectangle.h and Rectangle.cpp. Write in Rectangle.cpp implementations of methods in class Rectangle

Answer 2

Thank you guys so much. I have fixed my errors compiled and ran it and everything seems to be fine with it. So once again thank you. Also I put my.h file in my.cpp placeholder I am sorry about that. Here is my real.cpp file for any of you wondering.

 #include <iostream> #include "Rectangle.h" using namespace std; Rectangle::Rectangle(double len, double wid) { length = len; width = wid; } double getLength(); void Rectangle::setLength(double len) { length = len; } double getWidth(); void Rectangle::setWidth(double win) { width = win; } double Rectangle::getArea() { return width * length; }