我不确定为什么在尝试重载 = 运算符时会出现以下错误
error: passing ‘const MyCircle’ as ‘this’ argument of ‘double MyCircle::getRadius()’ discards qualifiers|
代码:
#include <iostream>
#define PI 3.14
using namespace std;
class MyCircle
{
public:
MyCircle();
MyCircle(int r);
MyCircle(const MyCircle& c);
void setRadius(double r);
double getRadius();
double getArea();
static void increaseInstanceCount();
static int getInstanceCount();
MyCircle operator=(const MyCircle &);
private:
double radius;
static int instanceCount;
};
int MyCircle::instanceCount = 0;
/**
1. A default constructor, that sets the radius to 0
**/
MyCircle::MyCircle()
{
radius = 0.0;
increaseInstanceCount();
}
/**
2. A one argument costructor that accepts an int and uses it to initialize the radius
**/
MyCircle::MyCircle(int r)
{
radius = r;
increaseInstanceCount();
}
/**
3. A copy constructor that accepts a Circle reference as an argument, and uses it to initialize radius
**/
MyCircle::MyCircle(const MyCircle& c)
{
radius = c.radius;
increaseInstanceCount();
}
void MyCircle::increaseInstanceCount()
{
instanceCount++;
}
int MyCircle::getInstanceCount()
{
return instanceCount;
}
void MyCircle::setRadius(double r)
{
radius = r;
}
double MyCircle::getRadius()
{
return radius;
}
double MyCircle::getArea()
{
return (radius * radius) * PI;
}
//overload = operator
MyCircle MyCircle::operator=(const MyCircle &rhs)
{
if(this == &rhs)
return *this;
radius = rhs.getRadius();
return *this;
}
int main()
{
MyCircle circle;
circle.setRadius(5.4);
MyCircle circle2;
circle2.setRadius(3.0);
MyCircle circle3;
circle3.setRadius(343.3);
cout << "Total instances: " << circle.getInstanceCount() << endl;
return 0;
}
最佳答案
你需要给 getRadius()
方法添加一个 const
限定符,比如
double MyCircle::getRadius() const
{
return radius;
}
这将限定要使用 const 对象调用的方法。您可能希望将此限定符添加到任何不更改成员变量的方法,以避免此类错误。
关于C++ 重载 = 运算符,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5811933/