blocks|key|1979360|text|这里混淆了两个概念："::“用于命名空间，但也用于调用静态方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1979361|entityMap^0|R|2|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

You are mixing up 2 concepts here:
"::" is used for namespaces, but also for calling static methods.

blocks|key|1979374|text|now()是一个static成员函数。这意味着函数本身没有隐藏的this指针。相反，它就像一个常规函数--只是类的一部分，以避免名称冲突。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1979375|(在您的示例中，THe+high_resolution_clock是类，chrono是命名空间。这两种方法都使用::来表示“我想从{命名空间，类}中得到一些东西)”|1979376|entityMap^0|0|5|8|6|W|4|0|C|L|10|6|1K|2|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|I|$]]

<code>now()</code> is a <code>static</code> member function. This means that the function itself doesn't have a hidden <code>this</code> pointer. Instead, it's just like a regular function - just part of the class to avoid name collisions. 

(THe <code>high_resolution_clock</code> is a class, <code>chrono</code> is a namespace, in your example. Both use <code>::</code> to indicate "I want something from inside {namespace, class})

blocks|key|1979382|text|你建议的语法没有错。它起作用了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1979383|然而，它创建一个对象，而::版本不创建任何对象。创建该对象似乎没有多大意义，因为没有必要这样做才能调用静态函数。因此，只调用静态函数而不创建对象就更简单了。|offset|length|style|CODE|1979384|entityMap^0|0|C|2|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

There is nothing wrong with the syntax you suggested. It works.

However it creates an object, whereas the <code>::</code> version does not create any object. There doesn't seem to be much point in creating that object since it is not necessary to do so in order to call the static function. So it is simpler to just call the static function without creating the object.

blocks|key|1281786|text|简单地说，::将名称与姓氏分开，而.将组件从子组件中分离出来。(请注意，在许多语言中，如C#、Java、D、.)没有这样的区别)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1281787|在第一个示例中，myarray是一个变量，其size()方法引用该特定变量。|1281788|array<int,5>+myarray_a,+myarray_b;
int+sa=myarray_a.size();
int+sb=myarray_b.size();|code-block|syntax|javascript|1281789|将分别给出myarray_a和b的大小(而不是array<int,5>，即使对于这种特殊情况，-due+-所有大小都是5)。|1281790|在第二个示例中，now()是类static的chrono::high_resolution_clock方法。|1281791|不管您是否有一个变量(以及chrono::high_resolution_clock类型的变量)，这都不重要。该函数不引用变量，但对所有相同类型的变量都是相同的(概念上只有一个now，不管您要求的是谁)。|1281792|因此，调用now()作为变量的一部分，通过完全限定其名称是相同的。|1281793|注意，size()函数的std::array是奇怪的：std::array的大小是编译时定义的，因此size()可能也是静态的。但是std::设计器允许它们作为成员(尽管constexpr，因此在编译时表达式中仍然可用)来保持与std::array或其他容器中相同的行为(在这些容器中，它必须是动态的，并且与变量相关联，因为每个大小在执行过程中都可能有所不同)。|1281794|entityMap^0|5|2|H|1|0|8|7|M|6|0|0|5|9|F|1|N|C|0|F|6|M|T|0|D|T|2G|3|0|5|5|0|3|6|C|A|R|A|1E|6|1U|5|2D|9|36|A|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1G|8|@$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1L|8|@$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]]|D|@]|E|$]]|$1|S|3|T|5|6|7|1Q|8|@$9|1R|A|1S|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1T|8|@$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]|$9|1Y|A|1Z|B|C]|$9|20|A|21|B|C]|$9|22|A|23|B|C]|$9|24|A|25|B|C]|$9|26|A|27|B|C]]|D|@]|E|$]]|$1|W|3|-4|5|6|7|28|8|@]|D|@]|E|$]]]|X|$]]

In simple terms, <code>::</code> separates names from surnames, while <code>.</code> separates components from sub-components. (Note that in many languages like C#, Java, D, ...) there is no such distinction)

In your fist example, <code>myarray</code> is a variable, whose <code>size()</code> method refer to that particular variable.

<pre><code>array&lt;int,5&gt; myarray_a, myarray_b;
int sa=myarray_a.size();
int sb=myarray_b.size();
</code></pre>

Will give the sizes of <code>myarray_a</code> and <code>b</code> respectively (not of <code>array&lt;int,5&gt;</code>, even if -due to this particular case- all sizes will be 5)

In the second example, now() is a <code>static</code> method of the class <code>chrono::high_resolution_clock</code>.

It doesn't matter if you have or not a variable (and how many) of type <code>chrono::high_resolution_clock</code>. That function does not refer to the variable but works the same for all variables of the same type (there is conceptually just one <code>now</code>, no matter who you ask to).

Because of this, call <code>now()</code> as part of a variable, of by fully qualifying its name is the same.

Note that, the <code>size()</code> function of <code>std::array</code> is strange: the size of <code>std::array</code> is compile time defined, hence <code>size()</code> could have been static as well. But <code>std::</code> designers let them as member (although <code>constexpr</code>, so still usable in compile time expressions) to retain the same behavior as in <code>std::array</code> or other containers (where it has to be dynamic, and associated to a variable, since each size can vary during execution)

I know that, given a class, say, std::array, which has a member function, say, size(), we can call on that member function via a ".", that is, in the following code,

<pre><code>array&lt;int,5&gt; myarray;
int s=myarray.size();
</code></pre>

s would be the integer representing the size of myarray. The tricky thing happens when member functions can also be called by the namespace operator "::". For example, I know that the following line of code is valid:

<pre><code>auto t=chrono::high_resolution_clock::now();
</code></pre>

Then, what's wrong with employing the syntax we originally used with array?

<pre><code>chrono::high_resolution_clock myclock;
auto t=myclock.now();
</code></pre>

:: versus . for member functions (C++)

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

我知道，给定一个类，例如，std::array，它有一个成员函数，比如size()，我们可以通过一个".“来调用该成员函数，也就是说，在下面的代码中，array<int,5> myarray;int s=myarray.size();S将是表示myarray大小的整数。当成员函数也可以被命名空间运算符"::“调用时，就...

问*对抗。用于成员函数(C++)
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问*对抗。用于成员函数(C++)EN