Question

我正在学习c ++中的重载函数，本书中的一个例子是行不通的。这是代码，

#include <iostream>
using namespace std;
//rectangle class declaration
class Rectangle
{
public:
    //constructors
    Rectangle(int width, int height);
    ~Rectangle(){}

    //overload class function drawShape
    void DrawShape() const;
    void DrawShape(int aWidth, int aHeight) const;

private:
    int itsWidth;
    int itsHeight;
};

//constructor implementation
Rectangle::Rectangle(int width, int height)
{
    itsWidth;
    itsHeight;
}


//overloaded DrawShape - takes no values
//Draws based on current class member values
void Rectangle::DrawShape() const
{
    DrawShape(itsWidth, itsHeight);
}


//overloaded DrawShape - takes two values
//Draws shape based on the parameters
void Rectangle::DrawShape(int width, int height) const
{
    for (int i = 0; i < height; i++)
    {
        for (int j = 0; j < width; j++)
        {
            cout << "*";
        }
        cout << "\n";
    }
}

//Driver program to demonstrate overloaded functions
int main()
{
    //Initialize a rectangle to 30, 5
    Rectangle theRect(30, 5);
    cout << "DrawShape(): \n";
    theRect.DrawShape();
    cout << "\nDrawShape(40, 2): \n";
    theRect.DrawShape(40, 2);
    system("pause");
    return 0;
}

我遇到的问题是将Rectangle theRect初始化为30,5不输出任何内容，但我知道该函数有效，因为它确实输出了40个矩形。

Answer 1

你的构造函数没有做任何事情，它应该是

//constructor implementation
Rectangle::Rectangle(int width, int height)
{
    itsWidth = width;
    itsHeight = height;
}

由于DrawShape是类Rectangle中的一个函数，它可能不应该接受任何参数，它应该使用对象的成员变量

void Rectangle::DrawShape() const
{
    for (int i = 0; i < itsHeight; i++)
    {
        for (int j = 0; j < itsWidth; j++)
        {
            cout << "*";
        }
        cout << "\n";
    }
}

请注意，您的构造函数有一个替代（和arguably preferred）语法，使用member initialization list

//constructor implementation
Rectangle::Rectangle(int width, int height)
: itsWidth{width}, itsHeight{height} {}

Answer 2

你的构造函数没有初始化任何东西，它应该是这样的：

//constructor implementation
Rectangle::Rectangle(int width, int height)
    : itsWidth(width)
    , itsHeight(height)
{
}

更改后，您的结果如下所示：

DrawShape(): 
******************************
******************************
******************************
******************************
******************************

DrawShape(40, 2): 
****************************************
****************************************

c ++重载函数问题

2 个答案: