精简多个elseif语句

Question

I am currently working on a project that uses keypad numbers as save location for a sensor (f_temp) and saves it into float array sensorData[], u8_key is the variable that recognizes the key-press. How can i improve this without using multiple else if statements?

void saveValue(void){
      if (u8_key == '1'){
            writeLCD(0x01,0,0,1); // clears LCD
            sensorData[0] = f_temp;
            outStringLCD("Saved to 1"); // writes to LCD for visual confirmation of value being saved and to what location on LCD
          }

         else if (u8_key == '2'){
            writeLCD(0x01,0,0,1);
            sensorData[1] = f_temp;
            outStringLCD("Saved to 2");
         }

        else if (u8_key == '3'){
            writeLCD(0x01,0,0,1);
            sensorData[2] = f_temp;
            outStringLCD("Saved to 3");
      }         
              else if (u8_key == '4'){
            writeLCD(0x01,0,0,1);
            sensorData[3] = f_temp;
            outStringLCD("Saved to 4");
      } 
        else if (u8_key == '5'){
            writeLCD(0x01,0,0,1);
            sensorData[4] = f_temp;
            outStringLCD("Saved to 5");
      } 
        else if (u8_key == '6'){
            writeLCD(0x01,0,0,1);
            sensorData[5] = f_temp;
            outStringLCD("Saved to 6");
      } 
        else if (u8_key == '7'){
            writeLCD(0x01,0,0,1);
            sensorData[6] = f_temp;
            outStringLCD("Saved to 7");

      } 
        else if (u8_key == '8'){
            writeLCD(0x01,0,0,1);
            sensorData[7] = f_temp;
            outStringLCD("Saved to 8");

      } 
        else if (u8_key == '9'){
            writeLCD(0x01,0,0,1);
            sensorData[8] = f_temp;
            outStringLCD("Saved to 9");

      } 
        else if (u8_key == '0'){
            writeLCD(0x01,0,0,1);
            sensorData[9] = f_temp;
            outStringLCD("Saved to 0");

      } 
        else if (u8_key == '*'){
            writeLCD(0x01,0,0,1);
            sensorData[10] = f_temp;
            outStringLCD("Saved to *");
      } 

Answer 1

the simplest fix is to use a switch...case statement such as

switch(u8_key)
{
    case '1':
        writeLCD(0x01,0,0,1); // clears LCD
        sensorData[0] = f_temp;
        outStringLCD("Saved to 1");
        break;

    case '2': 
        writeLCD(0x01,0,0,1); // clears LCD
        sensorData[1] = f_temp;
        outStringLCD("Saved to 2");
        break;
    ...

and so on. Notice you need that break statement to ensure that only one case is hit at a time.

EDIT: Note that Christian Gibbons' solution is more efficient and elegant, and you should use that. The switch statement should only be used if you need to do different things with each case.

Answer 2

The only special case that requires a conditional is '*' . As Lee Daniel Crocker pointed out, the decimal characters are represented sequentially, so you can reliably get the decimal represented by a character with simple math. '1' - '0' = 1 , and so on. The only special cases will be '0' , which is not filling the same index in your array sequentially as its value would suggest, and '*' , which is obviously not a digit. For '0' , that can be solved with modulo arithmetic. So with all that, here is a sample piece of code should perform the same as your function:

void saveValue(void){
        int index = ((u8_key - '0' + 9) %10);
        if (u8_key == '*') {
           index = 10;
        }
        writeLCD(0x01,0,0,1);
        sensorData[index] = f_temp;
        char buff[11] = "Saved to \0\0";
        buff[9] = u8_key;
        outStringLCD(buff);
}

Answer 3

My solution, created by observing all the cases and finding similarities between them:

if (('0' <= u8_key && '9' >= u8_key) || '*' == u8_key) {
       writeLCD(0x01, 0, 0, 1);
       const size_t idx = '*' == u8_key ? 10 : (u8_key - '0' + 9) % 10;
       sensorData[idx] = f_temp;
       const char buf[] = {'S','a','v','e','d',' ','t','o',' ',u8_key,'\0'};
       outStringLCD(buf);
}