C++ 圆形对象/getArea()

Question

我想写一个程序

• 定义一个包含五个圆对象的数组，其中使用参数化构造函数的随机类提供的随机数设置半径

• 定义第二个包含五个圆对象的数组，其中使用 random 类使用 setRadius 方法提供的随机数设置半径

• 使用 getArea()

显示每个数组中每个圆的面积

我需要帮助来使用 getArea() 方法显示每个数组中每个圆的面积，我需要访问每个数组中具有五个圆的半径值的数组，然后计算出面积 3.14 *半径 * 半径。然后将该区域显示到屏幕上。

另外，在做了一些研究之后，我是否需要实例化 Circle 对象 这是我在 Circle myCircle; 中输入的。然而它出现了一个错误说

1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall Circle::Circle(void)" (??0Circle@@QAE@XZ) referenced in function _main

Circle.h文件

#pragma once
#include <string>

class Circle 
{
private:
    float Radius;

public:
    Circle(); // initialised radius to 0
    Circle(float r); // accepts an argument and assign its value to the radius attribute
    void setRadius(float r); // sets radius to a value provided by its radius parameter (r)
    float getRadius(); // returns the radius of a circle
    float getArea(); // calculates and returns the areas of its circle
};

随机.h文件

#pragma once
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

class Random
{
public:
    static void initialiseSeed();
    // random number initialised
    // random number has been initialised to the current time.

    static int random(int lower, int upper);
    // this function will return a positive random number within a specific lower and 
    // upper boundary.
};

main.cpp 文件

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <iomanip>
using namespace std;

// Include header files
#include "Circle.h"
#include "Random.h"

int main()
{
    // Instantiate myCircle object
    //Circle myCircle;

    // Array 1
    // an array of five circles objects where radius is set using the random number
    // provided by the random class utilising the parameterised constructor

    int CircleArrayOne [5]; // store the numbers
    const int NUM = 5; // Display 5 random numbers

    srand(time(NULL)); // seed the generator

    // populate the array by calling the random function from the random class
    // within the lower and upper bounds

    for(int x = 0; x < NUM; ++x)
    {
        CircleArrayOne[x] = Random::random(1, 40); // assumed 0 and 40 as the bounds
    }

    // Below is the code I use to output the array to the screen to make sure
    // that is output the correct number of values and it generate number between 1 and 40
    // I am doing this to test the code above that populate the array within lower and upper
    // bounds

    cout << "Checking the radius in the Array 1." << endl;
    for(int i = 0; i < NUM; ++i) 
    {
        cout << CircleArrayOne[i] << endl;
    }

    // Array 2
    // a second array of five circles objects where radius is set using the random number 
    // provided by the random class utilising the setRadius method

    float CircleArrayTwo [5]; // store the numbers
    const int Number = 5; // Display 5 random numbers

    srand(time(NULL)); // seed the generator

    // populate the array with random numbers

    for(int i = 0; i < Number; ++i)
    {
        CircleArrayTwo[i] = rand()%100;
    }

    // Below is the code I use to output the array to the screen to make sure
    // that is output the correct number of values and it generate random values

    cout << "Checking the radius in the Array 2." << endl;
    for(int i = 0; i < Number; ++i)
    {
        cout << CircleArrayTwo[i] << endl;
    }

    // Display the area of each Circle within each array using getArea()

    cout << "\nThe area of each circle within array 1: " << endl;

    cout << "\nThe area of each circle within array 2: " << endl;

    // Display a message that indicates which set of circle has the largest 
    // combined area

    cout << "\nArray: " << "had the largest combined area." << endl;

    // Display a message that indicates which set contains the circle 
    // with the largest area

    cout << "\nArray: " << "contain the circle with the largest area.\n" << endl;

    system("PAUSE");
    return 0;
}

// Calling Circle(float r) from Circle Class
Circle::Circle(float r)
{
    if (r<=0)
    {
        cout << "An invalid radius has been detected." << endl;
        cout << "The radius has been set to 1.0" << endl;
        Radius = 1.0;
    }
    else
        Radius = r;
}

// Calling getArea() from Circle Class
float Circle::getArea()
{
    // Area = pi * radius * radius
    return 3.14 * Radius * Radius;
}

// Calling setRadius(float r) from Circle Class
void Circle::setRadius(float r)
{
    rand()%100;
    Radius = r;
}

// Calling getRadius() from Circle Class
float Circle::getRadius()
{
    return Radius;
}

// Calling random(int lower, int upper) from Random Class
int Random::random(int lower, int upper)
{
    int range = upper - lower + 1;
    return (rand() % range + lower);
}

// Calling initialiseSeed() from Random Class
void Random::initialiseSeed()
{
    srand((unsigned int)time(0));
    rand()%100;
}

如何使用 getArea() 函数获取每个数组中每个圆的面积

Answer 1

您还没有为Circle 的默认构造函数提供定义，添加

Circle::Circle() : Radius(0) {}

到 main.cpp。