C ++ 11变量初始化和声明 [英] C++11 Variable Initialization and Declaration

问题描述

使用C ++ 11提供了一种新的方法来初始化和声明变量。

原始

  int c_derived = 0; 
  

C ++ 11

  int modern {0}; 
  

每种方法的优点和缺点是什么？为什么要实现一个新的方法？

解决方案

你错了 - int modern





在C ++中，可以在C ++的旧版本中使用表单（带圆括号） +11，新表单使用大括号来提供统一的初始化，所以你说

  int modern {0}; 
  

这种新表单的主要优点是它可以一直使用到处。它清楚地表明，您正在初始化一个新对象，而不是调用函数，或者更糟糕的是，声明一个。 / p>

它还提供了与C风格（聚合）结构初始化的语法一致性，形式如下：

  struct A 
 {
 int a; int b; 
}; 
 
 A a = {1，2}; 
  

对于缩小数值类型的转换，还有更严格的规则

With C++11 came a new way to initialize and declare variables.

Original

int c_derived = 0;

C++11

int modern{0};

What are the pros and cons of each method, if there are any? Why implement a new method? Does the compiler do anything different?

解决方案

You're mistaken -- the int modern(0) form (with round brackets) was available in older versions of C++, and continues to be available in C++11.

In C++11, the new form uses curly brackets to provide uniform initialisation, so you say

int modern{0};

The main advantage of this new form is that it can be consistently used everywhere. It makes it clear that you're initialising a new object, rather than calling a function or, worse, declaring one.

It also provides syntactical consistency with C-style ("aggregate") struct initialisation, of the form

struct A
{
    int a; int b;
};

A a = { 1, 2 };

There are also more strict rules with regard to narrowing conversions of numeric types when the curly-bracket form is used.

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