如何将enum传入带switch case的函数？解决编译报错问题

错误原因 #

你当前的枚举声明enum{TOP, BOTTOM}motorGroup;是定义了一个匿名枚举类型，同时创建了一个名为motorGroup的变量，而非将motorGroup定义为枚举类型名。所以在函数参数里写motorGroup group时，编译器会把motorGroup当成变量，导致语法错误。

修复方案 #

有两种标准写法可以正确定义枚举类型，让函数参数和switch-case正常工作：

方案1：使用typedef定义枚举类型别名 #

直接把motorGroup定义成枚举类型的别名，函数参数可直接用motorGroup作为类型，写法更简洁：

typedef enum {TOP, BOTTOM} motorGroup;
long pulses;
int ppi = 0;
int dist = 0;
int speed;

void pulseCount()
{
  pulses++;
  dist = pulses / ppi;
}

void systemInit()
{
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  attachInterrupt(digitalPinToInterrupt(2), pulseCount, RISING);
}

void actuatorPush(motorGroup group, int speed)
{
  switch(group)
  {  
    case TOP:
    analogWrite(4, speed);
    analogWrite(5, 0);
    analogWrite(6, speed);
    analogWrite(7, 0);
    break;    

    case BOTTOM:
    analogWrite(8, speed);
    analogWrite(9, 0);
    analogWrite(10, speed);
    analogWrite(11, 0);
    break;
  }    
}

void actuatorPull(motorGroup group, int speed)
{
  switch(group)
  {  
    case TOP:
    analogWrite(4, 0);
    analogWrite(5, speed);
    analogWrite(6, 0);
    analogWrite(7, speed);
    break;    

    case BOTTOM:
    analogWrite(8, 0);
    analogWrite(9, speed);
    analogWrite(10, 0);
    analogWrite(11, speed);
    break;
  }    
}

方案2：显式命名枚举类型 #

先定义带名字的枚举类型，函数参数中使用enum motorGroup作为类型：

enum motorGroup {TOP, BOTTOM};
long pulses;
int ppi = 0;
int dist = 0;
int speed;

// 后续函数参数需修改为：
void actuatorPush(enum motorGroup group, int speed)
// actuatorPull函数参数做同样修改

说明 #

两种方案都能让编译器正确识别group是枚举类型参数，switch-case也能正常解析TOP和BOTTOM枚举值。

内容的提问来源于stack exchange，提问作者RGB Engineer