rephrase the if statement in Dart 2.0 using null - flutter

Question

I have following statement in flutter. weight is the text from _weightController i.e. _weightController.text
int.parse(weight).toString().isNotEmpty && int.parse(weight) > 0
But in Dart 2.0 it is not working properly. For empty TextField, it is giving the error.
====== Exception caught by gesture ==============================
The following FormatException was thrown while handling a gesture:
Invalid number (at character 1)
The code block is like this.
if (int.parse(weight).toString().isNotEmpty && int.parse(weight) > 0)
return int.parse(weight) * multiplier;
else
print('Error');

Answer 1

As an alternative to the other answer, you can use the tryParse() method:
Like parse except that this function returns null where a similar call to parse would throw a FormatException, and the source must still not be null.
If you use this approach, you should check the return value for null:
String weight ="";
int number = int.tryParse(weight);
if (number !=null){
print(number );
}
else
print("error");
Don't forget to also check the variable for null with weight ? "" or with weight != null

Answer 2

Try this:
if (weight != null && weight.isNotEmpty) {
return int.tryParse(weight) * multiplier;
} else {
print("CoolTag: error");
return -1;
}