Getting error parsing a value to an integer in flutter-CodePudding

I am having this code below

int? _trades = data['trades'] ?? 0;

so I want to parse data['trades'] to an integer so I did this

int? _trades = int.parse(data['trades']) ?? 0;

But I got this error:

The left operand can't be null, so the right operand is never executed.   Try removing the operator and the right operand.

CodePudding user response：

Generally we use ?? in dart when we expect a null value from source and we want to assign a fallback value.

But as mentioned by @omkar76 int.parse() does not return the null hence there is no point using ?? 0 at the end because it will never return null instead it will just throw an error.

In order to catch the error you can place try/catch around the int.parse() that way you'll be safely parse the code and your error will get disappear.

Example code

void main() {
  var data = {'trades': '2'};//sample data
  int trades = 0; //setting default value
  try {
    int trades = int.parse(data['trades']!);
  } catch (e) {
    print('[Catch] $e');
  }
  print(trades);
}

CodePudding user response：

int? _trades = data['trades'] ?? 0;

Int? Means the value can be null but you also added ?? Which means if its null then assign 0.

So you can either use

int? _trades = data['trades'];
//Or
int _trades = data['trades'] ?? 0;