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dartflutterdynamic-typing

Parse dynamic as int or fallback to a default value

I have a map with dynamic values, one of which can be an int, string or null (i.e. non-existing key).

I want to store this value in an int variable. The parsing I came up with ended up being quite cumbersome:

Map<String, dynamic> map = {'maxposts': null}; // or 23 or '42'

// Try to parse an int value or fall back to 0
int maxposts = (map['maxposts'] is int) 
    ? map['maxposts'] 
    : int.tryParse(map['maxposts'] ?? '0') ?? 0;

Is there a nicer way of doing such a "try-fallback" parsing?

Solution

  • You can abstract the operation into a function like

    int intOrStringValue(dynamic o) {
  if (o is String) o = int.tryParse(o);
  return o ?? 0;
}

    or 

    int intOrStringValue(dynamic o) =>
    (o is String ? int.tryParse(o) : o) ?? 0;

    It gets more readable when you don't repeat the map['maxposts'] expression throughout the logic.