C++ 成员初始值设定项列表问题：私有成员变量的声明顺序

Question

这是我在 Stack Overflow 上发布的第一个问题，希望有人能解释一下。所以基本上这两个类除了私有成员变量的顺序之外是一样的。输出是10 20 10 0我不明白为什么声明的顺序会影响输出。

#include <iostream>
using namespace std;

class MyClass{
public:
    MyClass(int value): b(value), a(b * 2){
        cout << b << " " << a << " ";
    }
private:
    int b;
    int a;
};

class YourClass{
public:
    YourClass(int value): d(value), c(d * 2){
        cout << d << " " << c << " ";
    }
private:
    int c;
    int d;
};

int main(){
    MyClass obj(10);
    YourClass OBJ(10);
}

Answer 1

Class 成员按照声明的顺序进行初始化。

Initialization Order of Class Data Members

#include <iostream>

class MyClass{
public:
    MyClass(int value): b(value++), a(value++){
        std::cout << b << " " << a << " " << std::endl;
    }
private:
    int b;
    int a;
};

class YourClass{
public:
    YourClass(int value): b(value++), a(value++){
        std::cout << b << " " << a << " " << std::endl;
    }
private:
    int a;
    int b;

};

int main(){
    MyClass obj(10);
    YourClass OBJ(10);
}

输出：

10 11
11 10

C++ 成员初始值设定项列表问题：私有成员变量的声明顺序

C++ Member Initializer Lists Problem: Declaration Order on Private Member Variables

c++

class

private

member

initializer