这些对象初始化有什么区别？ [重复]

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• Is there a difference between copy initialization and direct initialization? 8 answers
• 复制初始化和直接初始化之间有区别吗？ 8个答案

There are two type of object initialisation using copy constructor:

使用复制构造函数有两种类型的对象初始化：

Class object2(val1, val2); // <--- (1)

Same can be done by copying the contents of another class:

同样可以通过复制另一个类的内容来完成：

Class object1(val1, val2);
Class object2 = object1;  // <--- (2)

What is the difference between (1) and (2) ? Are they explicit calls and implicit calls or does it have to do with operator overloading?

（1）和（2）之间有什么区别？它们是显式调用和隐式调用还是与运算符重载有关？

2 个解决方案

#1

Both constructs use constructors, but different constructors. First is a constructor taking two arguments, second is normally the copy constructor (can be defaulted). The explicit declarations should be like:

两个构造都使用构造函数，但使用不同的构造函数。首先是一个带有两个参数的构造函数，第二个通常是复制构造函数（可以是默认的）。显式声明应该是：

class Class {
    // constructor taking 2 args
    Class(int val1, const std::string& val2);
    // copy ctor
    Class(const Class& other);

    /* you could optionaly have a move ctor:
    Class(Class&& other); */
    ...
};

#2

Here

这里

1. case 1

Class object2(val1, val2);

will call the constructor with two arguments

将使用两个参数调用构造函数

Class(type a, type b);

2. case 2

Class object2 = object1;

will call the copy constructor

将调用复制构造函数

Class(const Class&);

Demo

演示