结构构造函数语法 [英] Struct Constructor Syntax

问题描述

可能的重复:
C++ 构造函数名称后面的冒号有什么作用?

我在网上找到了下面的例子，但是构造函数的语法让我有点困惑，尤其是 : 符号.谁能给我一个简短的解释?谢谢.

I found the example below online however the syntax for the constructor confuses me a little bit especially the : symbol. Could anyone please give me a brief explanation ? Thanks.

struct TestStruct {
    int id;
    TestStruct() : id(42)
    {
    }
};

推荐答案

构造函数在调用时将 id 初始化为 42.它被称为初始化列表.

The constructor initializes id to 42 when it's called. It's called an initliazation list.

在你的例子中，它相当于

In your example, it is equivalent to

struct TestStruct {
    int id;
    TestStruct()
    {
        id = 42;
    }
};

你也可以和几个成员一起做

You can do it with several members as well

struct TestStruct {
    int id;
    double number; 
    TestStruct() : id(42), number(4.1)
    {
    }
};

当构造函数的唯一目的是初始化成员变量时很有用

It's useful when your constructor's only purpose is initializing member variables

struct TestStruct {
    int id;
    double number; 
    TestStruct(int anInt, double aDouble) : id(anInt), number(aDouble) { }
};

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