Question

c++高手进,关于 no matching function for call to

#include<iostream>
#include<math.h>
using namespace std;
class Point
{
private:
float x,y;
public:
Point(float x0,float y0){x=x0;y=y0;};

float getx(){return x;};
float gety(){return y;};
void setPoint(float x,float y);
float distance(Point a,Point b);
};

void Point:: setPoint(float x0,float y0)
{
x=x0;
y=y0;
}
float Point:: distance(Point a,Point b)
{
float d;
d=sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
return d;
}
class Rectangle
{
private:
Point a,b;//a表示左上角那个点，b表示右下角那个点
public:
Rectangle(float x1,float y1,float x2,float y2);
float size(Rectangle t);
void setRec(void);
};

Rectangle::Rectangle(float x1,float y1,float x2,float y2)
{
a.setPoint(x1,y1);
b.setPoint(x2,y2);
}
//到这里就出问题了, no matching function for call to`Point::Point()'
float Rectangle::size(Rectangle t)
{
float s;
s=(b.getx()-a.getx())*(a.gety()-b.gety());
return s;
}

void Rectangle::setRec(void)
{
float x1,y1,x2,y2;
cout<<"Please input the point in left and up."<<endl;
cin>>x1>>y1;
cout<<"Please input the point in right and down."<<endl;
cin>>x2>>y2;

a.setPoint(x1,y1);
b.setPoint(x2,y2);
}

int main()
{
float size;
Rectangle A(0,0,-1,-1);
A.setRec();
size=A.size(A);
cout<<"The size is "<<size;
system("pause");
return 0;
}

Answer 1

没有匹配的构造函数。因为你替换了Point的默认构造函数，在Rectangle::Rectangle(float x1,float y1,float x2,float y2)
{
a.setPoint(x1,y1);
b.setPoint(x2,y2);
}
没有办法初始化，解决办法有两个，第一个是用Rectangle::Rectangle(float x1,float y1,float x2,float y2)：a(0,0）,b（0,0）手动初始化
第二个是添加一个无参数的Point构造函数

Answer 2

问题:
a.setPoint(x1,y1); b.setPoint(x2,y2);
以上两个操作的前提是a,b为Point类的实例,但之前你并没有用Point类的构造函数对a,b进行构造

解决办法:
将Point类的构造函数的参数列表中添加默认参数
Point(float x0,float y0){x=x0;y=y0;};
改为Point(float x0=0.0,float y0=0.0){x=x0;y=y0;};