混淆与直接初始化和副本初始化 [英] Confused with direct initialization and copy initialization

问题描述

我对以下概念感到困惑：

I am confused with followed concepts:

string str="123";

有些书说：=是复制初始化，

Some books say that: using "=" is copy initialization,

但是一些文章说： string str =123与 string str（123）。毫无疑问，str（123）是直接初始化。

but some articles say: string str="123" is same as string str("123"). There is no doubt str("123") is directly initialization.

因此， string str =123; ？

如何判断哪个是复制初始化或直接初始化？

How to judge which is copy initialization or directly initialization?

推荐答案

：

• T x = y;

T x（y）; em> direct-initialization 。

T x(y); is direct-initialization.

。发生什么取决于 T 是什么类型。对于原始类型（例如 int s），两者是完全相同的。对于类类型（例如 std :: string ），这两个实际上是相同的，虽然copy-initialization要求一个拷贝构造函数是可访问的和非显式的但实际上不会被调用）。

This is true for any type T. What happens exactly depends on what sort of type T is. For primitive types (e.g. ints), the two are exactly the same. For class-types (such as std::string), the two are practically the same, though copy-initialization requires that a copy-constructor be accessible and non-explicit (though it will not actually be called in practice).

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