#include <stdbool.h>

bool setValue = true;  

for (int i = 0; i < numOfIterations; i++){
   if (this happens && setValue){
       value = i;  //trying to save that particular position
       setValue = false; // Now that setValue is false
                         // variable "value" will not be set again,
                         // even if "this happens" is true
   } // End of if
} // End of For-loop

最简单的方法是

for (int i = 0; i < numOfIterations; i++){
   if (this happens && i == 0){
   value = i;
   }
}

for (int i = 0; i < numOfIterations; i++){
   if (this happens && i == 0) {  //that means if i is equal to 0 and your condition is true, code will be executed
       value = i;  //trying to save that particular position
   }
}