C++构造函数初始化的问题

Question

class D{
int x,y;
public:
D(){
x=0;
y=0;
}
};和
class D{
int x,y;
public:
D(int x=0,int y=0){
}
};的区别

Answer 1

这个例子可能能帮助你

#include <iostream>
using namespace std;
class Box {
public:
    Box(int h = 2, int w = 2, int l = 2);//在声明构造函数时指定默认参数
    int volume();
private:
    int height, width, length;
};
Box::Box(int h, int w, int len) {//在定义函数时可以不指定默认参数
    height = h;
    width = w;
    length = len;
}
int Box::volume() {
    return height * width*length;
}
int main() {
    Box box1(1);//不指定第2、3个实参
    cout << "box1's volume: " << box1.volume() << endl;
    Box box2(1, 3);// 不指定第3个实参
    cout << "box2's volume: " << box2.volume() << endl;
    Box box3;
    cout << "box3's volume:" << box3.volume() << endl;
    return 0;
}