尝试在类中定义静态常量变量 [英] Trying to define a static constant variable in a class

问题描述

我在类<$ c中将变量 adc_cmd [9] 定义为静态const无符号字符 $ c> ADC 在私有下。因为它是一个常数，所以我想只在它自己的类中定义它，但这显然不起作用：

I am defining a variable adc_cmd[9] as a static const unsigned char in my class ADC under private. Since it is a constant I thought I would just define it inside the class it self, but that didn't work apparently:

#pragma once

class ADC{
private:
    static const unsigned char adc_cmd[9] = { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };
//...
};

错误：

error: a brace-enclosed initializer is not allowed here before '{' token
error: invalid in-class initialization of static data member of non-integral type 'const unsigned char [9]'

...

因此，我尝试使用以下方法使该类退出该类： static const unsigned char ADC :: adc_cmd [9] = {0x87、0xC7、0x97、0xD7、0xA7、0xE7、0xB7、0xF7， 0x00}; ，但是会产生此错误：

So I tried bringing the line out of the class with: static const unsigned char ADC::adc_cmd[9] = { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };, but that yielded this error:

error: 'static' may not be used when defining (as opposed to declaring) a static data member
error: 'const unsigned char ADC::adc_cmd [9]' is not a static member of 'class ADC'

我显然没有正确地声明这一点。声明此内容的正确方法是什么？

I obviously am not declaring this properly. What is the correct way to declare this?

推荐答案

您声明它在类体内：

class ADC{
private:
    static const unsigned char adc_cmd[9];
//...
};

和 define （并初始化）它在外部（仅一次）任何外部链接定义）：

and define (and initialize) it outside (just once, as for any external-linkage definition):

const unsigned char ADC::adc_cmd[9] = { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };

不写 static ，错误消息。

（不要问我为什么在这里禁止 static 的解释，我总是发现各种限定词重复规则完全不合逻辑）

(don't ask me for an explanation of why here static is forbidden, I always found the various "repetition of qualifiers" rules completely illogic)

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