Flutter Can't Convert String To Double - json

Question

Hello everyone i have a simple function that will receive double from my server and then it should parse this decimal to double and add it to the total amount variable
for (int i = 0; i < purchase.length; i++){
currentTotalPrice = currentTotalPrice + purchase[i]['total_price'];
}
the thing is i am receiving the total price which is a decimal in the database in a String format and when i try to do something like (purchase[i]['total_price']).toDouble(); the compiler throws
Class 'String' has no instance method 'toDouble'.
Receiver: "15.00"
Tried calling: toDouble()
i don't know why in other parts of my code it worked correctly
this is how i am receiving the data
Future<List> _fetchPurchases() async {
final prefs = await SharedPreferences.getInstance();
String accessToken = prefs.getString("accessToken");
final response = await http.get(
'$webSiteUrl/api/admin/purchases/${article['id']}/$_billNumber',
headers: <String, String>{
'Content-Type': 'application/json;',
'Authorization': 'Bearer $accessToken',
},
);
if(response.statusCode == 200){
List purchases = json.decode(response.body);
return purchases;
}else{
return showErrorMessage(context);
}
}
Note: I am Aware of the Constructor solution where you create a class and then factory the data to custom dart object but for some circumstances i can't do that unless i refactor a very large part of the code so if there is a direct way like toDouble() method it would be the best solution

Answer 1

Indeed toDouble does not exist in the String class, but if you must use it, you can create an extension and import it, something like this
extension NumberParsing on String {
double toDouble() {
return double.parse(this);
}
}
check this gist https://gist.github.com/fcontreras/d5095da7daa0ce24e0f3cb157b91e97f