C++拷贝函数的小结,关于变量的作用域等---ShinePans

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#include <iostream>using namespace std;class circle{private:double r0;public:circle(double r){r0 = r;cout << r << "调用了球体的初始化的函数\n";}circle(const circle &t){r0 = t.r0;cout << "r=" << r0 << "调用了球体的复制的函数\n";}//double get_rr(){return r;}double getArea(){cout << "球体的表面积：" << 4 * 3.14*r0*r0;return 4 * 3.14*r0*r0;}};class Rectangle{private:double length;double width;double height;public:Rectangle(double a, double b, double c){length = a;width = b;height = c;cout << length << "," << width << "," << height << ",调用了长方体的初始化的函数\n";}Rectangle(Rectangle &n){length = n.length;width = n.width;height = n.height;cout << height << "调用了长方体的复制函数\n";}double getArea(){return (2 * length*width + 2 * length*height + 2 * width*height);}};class Whole{private:circle p1;Rectangle p2;double all_area;public:Whole(circle xp1, Rectangle xp2);};Whole::Whole(circle xp1, Rectangle xp2) :p2(xp2), p1(xp1){double area1 = 2 * p1.getArea();cout << "两个球体的表面积是：" << area1 << endl;double area2 = p2.getArea();cout << "长方体的表面积是：" << area2 << endl;all_area = area1 + area2;cout << "输出总的表面积:" << all_area << endl;}/*Whole::Whole(Whole &p):p1(p.p1),p2(p.p2){all_area=p.area1+p.area2;}/*Whole::Whole(Whole &p4):p(p4.p1),p(p4.p2){cout<<"输出总的表面积:";area=p4.area;}*/int main(){double m;cout << "请输入m的值:";cin >> m;double rr = m / 2;circle xp1(rr);Rectangle xp2(2 * m, m, m);Whole(xp1, xp2);system("pause");return 0;}

对用拷贝函数,有一个很重要的容易错误的地方:

在类中定义一个变量时:

如我在 class circle中定义一个 private : double r,如果下面全部使用r ,那么程序将会识别错误,会使用没有初始化的r,所以最好定义r0,后面传入的使用r,

下面是使用r的代码:

#include <iostream>using namespace std;class circle{private:double r;public:circle(double r){r=r;cout<<r<<"调用了球体的初始化的函数\n";}circle(circle & t){     r=t.r;    cout<<"r="<<r<<"调用了球体的复制的函数\n";}//double get_rr(){return r;}double getArea(){cout<<"球体的表面积："<<4*3.14*r*r;return 4*3.14*r*r; }};class Rectangle{private:double length;double width;double height;public:Rectangle(double a,double b,double c){length=a;width=b;height=c;cout<<length<<","<<width<<","<<height<<",调用了长方体的初始化的函数\n";}Rectangle(Rectangle &n){    length=n.length;width=n.width;height=n.height;cout<<height<<"调用了长方体的复制函数\n";}double getArea(){return (2*length*width+2*length*height+2*width*height);}}; class Whole{private:circle p1;Rectangle p2;double all_area;public:Whole(circle xp1,Rectangle xp2);  };Whole::Whole(circle xp1,Rectangle xp2):p2(xp2),p1(xp1){double area1=2*p1.getArea();cout<<"两个球体的表面积是："<<area1<<endl;double area2=p2.getArea();    cout<<"长方体的表面积是："<<area2<<endl;all_area=area1+area2;cout<<"输出总的表面积:"<<all_area<<endl;}/*Whole::Whole(Whole &p):p1(p.p1),p2(p.p2){all_area=p.area1+p.area2;}/*Whole::Whole(Whole &p4):p(p4.p1),p(p4.p2){cout<<"输出总的表面积:";area=p4.area;}*/int main(){double m; cout<<"请输入m的值:";cin>>m;double rr=m/2; circle xp1(rr);    Rectangle xp2(2*m,m,m);Whole(xp1,xp2);return 0;}

运行结果:

是错误的

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