How to store a return value in variable flutter

I need a little help.

I have this function in another file and i want to store the return value in a variable, because i dont want to repeat the same code again and again and I want to reuse it as many times I want.

here is the code in another file.

double dropDownIf(dropDownVal, finalVal, valParsed) {

  if(dropDownVal == 'm'){
        finalVal = valParsed;
      } else if(dropDownVal == 'cm'){
        finalVal = valParsed/100;
      } else if(dropDownVal == 'mm'){
        finalVal = valParsed/1000;
      }
      print('here is the updated value $finalVal');
   return finalVal;
}

as you can see that it show the return value in debug console but it doesnt show the value in another page in which i am using this code.

here is the code on another page.

dropDownIf(dropDownValueL, finalLength, lengthParsed);
      
      print(finalLength);

here in this page, the print function shows 0, I have declared the double finalLength = 0; in the beginning of the file. so the print shows 0 instead of the updated value.

the middle value in the dropDownIf function is the return value but it doesnt work.

>Solution :

You need to store the return value of the method in a variable, then use it:

double returnValue = dropDownIf(dropDownValueL, finalLength, lengthParsed);
 print(returnValue);