私有的成員和受保護的成員不能使用直接成員訪問運算子 (.) 來直接訪問。

1、問題程式碼

#include <iostream>
using namespace std;

class  Box
{
private:
	double length;   //長度
	double width;    //寬度
	double height;   //高度
};

int main()
{
	Box box1;
	Box box2;

	double volume = 0;

	//box1
	box1.length = 5;
	box1.width  = 6;
	box1.height = 7;

	//box2
	box2.length = 10;
	box2.width  = 11;
	box2.height = 12;

	volume = box1.height*box1.length*box1.width;
	cout<<volume<<endl;

	volume = box2.height*box2.length*box2.width;
	cout<<volume<<endl;

	system("pause");
	return 0;
}
 

2、修改後的程式碼

#include <iostream>
using namespace std;

class  Box
{
public:
	double length;   //長度
	double width;    //寬度
	double height;   //高度
};

int main()
{
	Box box1;
	Box box2;

	double volume = 0;

	//box1
	box1.length = 5;
	box1.width  = 6;
	box1.height = 7;

	//box2
	box2.length = 10;
	box2.width  = 11;
	box2.height = 12;

	volume = box1.height*box1.length*box1.width;
	cout<<volume<<endl;

	volume = box2.height*box2.length*box2.width;
	cout<<volume<<endl;

	system("pause");
	return 0;
}
 

結果：