在C的typedef枚举解释 [英] typedef enum explanation in c

问题描述

我在看一个微控制器上的ADC的头文件和下面的code是它。

I'm looking at a header file for an ADC on a micro controller and the following code is in it.

/**
 * ADC channels type.
*/

typedef enum {
    ADC_CH_0,
    ADC_CH_1,
    ADC_CH_2,
    ADC_CH_3,
    ADC_CH_4,
    ADC_CH_5,
    ADC_CH_6, 
} adc_channel_t;

而在main.c中的ADC有code的以下行

And in the main.c for the ADC there is the following line of code

adc_channel_t channels[] = {ADC_CH_4, ADC_CH_5};

我想知道为什么你需要为ADC宣布新的数据类型？又是什么类型定义枚举意味着什么呢？

I was wondering why would you need declare new data types for the ADC? and what does typedef enum mean?

感谢

推荐答案

作为补充由ARTM的答案的typedef 在<$ C $前面添加C>枚举，以缓解使用的枚举。了宣言看上去像这个：

As a complement to the answer by artm the typedef is added in front of the enum, to ease the use of the enum. Had the declaration looked like this instead:

enum adc_channel_t {
    ADC_CH_0,
    ADC_CH_1,
    ADC_CH_2,
    ADC_CH_3,
    ADC_CH_4,
    ADC_CH_5,
    ADC_CH_6, 
};

然后行 adc_channel_t频道[] = {ADC_CH_4，ADC_CH_5}; 将不得不写为：

enum adc_channel_t channels[] = {ADC_CH_4, ADC_CH_5};

的的typedef 让我们忽略了枚举在每次使用的类型。

The typedef allows us to ignore the enum at every use of the type.

使用有用的常量往往是$ pferred了幻数P $，虽然这似乎在这种情况下，常量给一点额外的信息有点怪。因为枚举作为额外的说明但它会是有用的。比如你的IDE将期望类型的值 adc_channel_t 将能够建议道： ADC_CH_0 到 ADC_CH_6 这可能是值的有效范围，而不是简单地告诉你使用一个号码。

Using useful constants is often preferred over "magic numbers", though it might seem a bit strange in this case the constants give little extra information. It can however be useful since the enumerator serves as extra description. For instance your IDE which will expect a value of type adc_channel_t will be able to suggest the channels: ADC_CH_0 through ADC_CH_6 that might be the valid range of values, instead of simply telling you to use a number.

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