C++拷贝函数的小结,关于变量的作用域等---ShinePans

#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
";
	}
	circle(const circle &t){
		r0 = t.r0;
		cout << "r=" << r0 << "调用了球体的复制的函数
";
	}
	//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
";
	}

	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
";
	}
	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,有一个非常重要的easy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,假设以下所有使用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,

以下是使用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
";
		}
		circle(circle & t){
	     r=t.r;
	    cout<<"r="<<r<<"调用了球体的复制的函数
";
}
		//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
";
		}
		
		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
";
}
		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;
}

执行结果:

是错误的