CODEWITHSUNDEEP
flutter
Nitneuq
Nitneuq

Reputation: 5012

How to calcul a sum of string list in flutter?

I use texfield to add number. After this I save in sharepreference the value in List

I search to make an addition of each value saved in this List

I tried this, but it doesn't works.

  load_list()async{
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {

      stringList = prefs.getStringList("list");


     sum = stringList.reduce((value, element) => value + element);

    });

  }

Upvotes: 1

Views: 1082

Answers (1)

Igor Kharakhordin
Igor Kharakhordin

Reputation: 9903

reduce returns the same type as the type in the collection, so you should use fold instead.

final List<String> stringList = prefs.getStringList("list") ?? [];
final int sum = stringList.fold<int>(0, (prev, value) => prev + int.parse(value));

To make it completely null-safe:

final int sum = stringList.fold<int>(0, (prev, value) => prev + (int.tryParse(value ?? '0') ?? 0));

Upvotes: 5

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