Why can't I convert a Number into a Double?

Question

weight is a field (Number in Firestore), set as 100.

int weight = json['weight'];
double weight = json['weight'];

int weight works fine, returns 100 as expected, but double weight crashes (Object.noSuchMethod exception) rather than returning 100.0, which is what I expected.

However, the following works:

num weight = json['weight'];
num.toDouble();

Answer 1

You can Parse the data Like given below:

Here document is a Map<String,dynamic>

double opening = double.tryParse(document['opening'].toString());

Answer 2

You can do it in one line:

 double weight = (json['weight'] as num).toDouble();