3-4 初始化列表操作

初始化列表操作实际上就是构造函数在初始化成员时的一个语法糖。
例如传统方法初始化:

#include <iostream>
#include <string>
using namespace std;
class Person {
public:
    Person(int a, int b, int c) {
        m_a = a;
        m_b = b;
        m_c = c;
    }
    int m_a;
    int m_b;
    int m_c;
};
void Example() {
    Person p1(10, 20, 30);
    cout << "m_a = " << p1.m_a << endl;
    cout << "m_b = " << p1.m_b << endl;
    cout << "m_c = " << p1.m_c << endl;
}
int main()
{
    Example();
    return 0;
}

列表化：简化后的

#include <iostream>
#include <string>
using namespace std;
class Person {
public:
    Person() : m_a(10), m_b(20), m_c(30) {}
    int m_a;
    int m_b;
    int m_c;
};
void Example() {
    Person p1;
    cout << "m_a = " << p1.m_a << endl;
    cout << "m_b = " << p1.m_b << endl;
    cout << "m_c = " << p1.m_c << endl;
}
int main()
{
    Example();
    return 0;
}

或者赋值的形式可以写成

#include <iostream>
#include <string>
using namespace std;
class Person {
public:
    Person(int a,int b,int c) : m_a(a), m_b(b), m_c(c) {}
    int m_a;
    int m_b;
    int m_c;
};
void Example() {
    Person p1(10,20,30);
    cout << "m_a = " << p1.m_a << endl;
    cout << "m_b = " << p1.m_b << endl;
    cout << "m_c = " << p1.m_c << endl;
}
int main()
{
    Example();
    return 0;
}