如何将类中的 Int 函数设置为等于 Main 中的 Int

Question

I have designed functions for getLength, getWidth, and getArea and I need to assign them to int values in my main function but I do not know how.

I have posted my header, implementation, and main.cpp files below.

Please adivse.

Ty.

Header File

#ifndef RECTANGLE_H
#define RECTANGLE_H

class Rectangle
{
    Rectangle();
public:
    int getLength;
    int getWidth();
    int getArea(int x, int y)
};
#endif

Implementation File

#include "Rectangle.h"
#include <iostream>
using namespace std;

int Rectangle::getLength()
{
    int x = 0;
    cout << "Enter Length: ";
    cin >> x;

    return x;
}

int Rectangle::getWidth()
{
    int x = 0;
    cout << "Enter Width: ";
    cin >> x;

    return x;

}

int Rectangle::getArea(int x, int y)
{
    int area = x * y;
    return area;
}

This is where I begin running into issues. The functions return an integer, but I do not know how to be able to assign the return integer to an int value.

#include "Rectangle.h"
#include "Rectangle.cpp"
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int area, length, width = 0;

    vector <int> myVector;
    cout << "Lets Make Some Rectangles: " << endl;

    for (int i = 0; i < 5; i++) {
        length = Rectangle::getLength();
        width = Rectangle::getWidth();

        area = Rectangle::getArea(length,width);

        myVector.push_back(area);
    }

    int largest = 0;

    for (int i = 0; i < 5; i++) {
        if (myVector[i] >= myVector[i + 1]) {
            largest = myVector[i];
        }
    }
    cout << "The Largest Rectangle Has an Area of: " << largest;
    system("pause");
    return 0;
}

Answer 1

One can call the member function in this way Rectangle::getLength(); only when getLength(); is declared static inside class Rectangle .

If member functions are not declared static then they can be accessed via object of the class.

Rectangle obj;
length = obj.getLength();

Also, you are crossing the valid bounds of vector myVector . You have inserted 5 elements in vector (from index 0 to 4) and trying to access 6th element myVector[5] via myVector[i] >= myVector[i + 1] when i = 4 .

Correct way to find largest:

int largest = myVector[0];

for (int i = 1; i < myVector.size(); i++) {
    if (largest > myVector[i]) {
        largest = myVector[i];
    }
}

Answer 2

As far as my knowledge with C++ goes, you need to create member variables which will hold the data(width, length), if you need create constructor which will take parameters for those memeber variables:

Rectangle(int width, int length){
    m_width = width;
    m_length = length;
}

notice member variables m_width and m_length

and create object, which will hold the data using constructor. ie

Rectangle myRectangle = Rectangle(5,5)