string("abc") 是否返回任何内容? [英] Does string("abc") return anything?

问题描述

像这样:

#include <iostream>
using namespace std;
int main()
{
    if ( string( "abc" ).size() == 3 )
        cout << "equ." << endl;
    return 0;
}

string("abc") 是否返回任何内容?如果是，那是值还是引用?

Does string("abc") return anything? If it does, that's a value or a reference?

推荐答案

类构造函数没有指定返回类型，也没有 return 语句.但是它们确实具有隐式返回类型 - 与声明它们的类相同，并且构造函数返回"刚刚构造的对象.

Class constructors do not have specified return type, and do not have return statement. But they do have implicit return type - same as class in which they are declared and constructor "returns" just constructed object.

T() 调用默认构造函数并返回"类型为 T 的匿名 prvalue(绑定到 T&&).它的生命周期是使用它的表达式的生命周期.它是可修改的.

T() calls default constructor and "returns" anonymous prvalue of type T (which binds to T&&). Its lifetime is lifetime of expression in which it is used. It is modifiable.

使用示例:

int()                                           // 0
(string()+=string("123")+="abc").substr(1,3)    // "23a"

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