CODEWITHSUNDEEP
dartnumber-formatting
matth3o
matth3o

Reputation: 3689

Dart - NumberFormat

Is there a way with NumberFormat to display :

Thanks for your help.

Upvotes: 39

Views: 59176

Answers (8)

Tommy Elliott
Tommy Elliott

Reputation: 491

Here is a flexible function that nicely rounds and removes trailing zeros after the decimal point to resolve double's imperfections. This doesn't handle the strictly 0 or 2 decimal points scenario from the question, but rather is a more general formatting for double numbers that may be useful for others to consider.

The verbose value can be changed to fit precision needs.

void main() {
  for (double i = 0; i < 10; i += 0.3) {
    print(i);
    print(_formatDouble(i));
  }
}

//Creates nicely formatted number string without trailing decimal zeros.
String _formatDouble(double value) {
  //this also rounds (so 0.8999999999999999 becomes '0.9000')
  var verbose = value.toStringAsFixed(4);
  var trimmed = verbose;
  //trim all trailing 0's after the decimal point (and the decimal point if applicable)
  for (var i = verbose.length - 1; i > 0; i--) {
    if (trimmed[i] != '0' && trimmed[i] != '.' || !trimmed.contains('.')) {
      break;
    }
    trimmed = trimmed.substring(0, i);
  }
  return trimmed;
}

prints output:

0
0
0.3
0.3
0.6
0.6
0.8999999999999999
0.9
1.2
1.2
1.5
1.5
1.8
1.8
2.1
2.1
2.4
2.4
2.6999999999999997
2.7
2.9999999999999996
3
3.2999999999999994
3.3
3.599999999999999
3.6
3.899999999999999
3.9
4.199999999999999
4.2
4.499999999999999
4.5
4.799999999999999
4.8
5.099999999999999
5.1
5.399999999999999
5.4
5.699999999999998
5.7
5.999999999999998
6
6.299999999999998
6.3
6.599999999999998
6.6
6.899999999999998
6.9
7.1999999999999975
7.2
7.499999999999997
7.5
7.799999999999997
7.8
8.099999999999998
8.1
8.399999999999999
8.4
8.7
8.7
9
9
9.3
9.3
9.600000000000001
9.6
9.900000000000002
9.9

Upvotes: 0

Ber
Ber

Reputation: 41813

An alternate solution, working on the string output of NumberFormat:

final f = NumberFormat("###.00");
print(f.format(15.01).replaceAll('.00', ''));
print(f.format(15.00).replaceAll('.00', ''));

Upvotes: 0

BIBIN M PANICKER
BIBIN M PANICKER

Reputation: 1

This will work.

main() {
  double n1 = 15.00;
  double n2 = 15.50; 

  print(_formatDecimal(n1));
  print(_formatDecimal(n2));
}

_formatDecimal(double value) {
  if (value % 1 == 0) return value.toStringAsFixed(0).toString();
  return value.toString();
}

Output:

15
15.5

Upvotes: 0

Durdu
Durdu

Reputation: 4849

Maybe you don't want use NumberFormat:

class DoubleToString {
  String format(double toFormat) {
    return (toFormat * 10) % 10 != 0 ?
      '$toFormat' :
      '${toFormat.toInt()}';
  }
}

Upvotes: 1

Anatolii Kosorukov
Anatolii Kosorukov

Reputation: 960

A variant of double value formatting:

void main (){
  final n1 = 15.00;
  final n2 = 15.50;
  print(format(n1));
  print(format(n2));
}
String format(double n) {
  final fraction = n - n.toInt();
  if (fraction == 0.0) {
    return n.toString();
  }
  var twoDigitFraction = (fraction * 100).truncateToDouble().toInt();
  return '${n.toInt()}.$twoDigitFraction';
}

Upvotes: 0

Alan Knight
Alan Knight

Reputation: 2971

Not very easily. Interpreting what you want as printing zero decimal places if it's an integer value and precisely two if it's a float, you could do

var forInts = new NumberFormat();
var forFractions = new NumberFormat();

forFractions.minimumFractionDigits = 2;
forFractions.maximumFractionDigits = 2;

format(num n) => 
    n == n.truncate() ? forInts.format(n) : forFractions.format(n);

print(format(15.50));
print(format(15.0));

But there's little advantage in using NumberFormat for this unless you want the result to print differently for different locales.

Upvotes: 4

Kul
Kul

Reputation: 1239

Edit: The solution posted by Martin seens to be a better one

I don't think this can be done directly. You'll most likely need something like this:

final f = new NumberFormat("###.00");

String format(num n) {
  final s = f.format(n);
  return s.endsWith('00') ? s.substring(0, s.length - 3) : s;
}

Upvotes: 7

martin
martin

Reputation: 96889

Actually, I think it's easier to go with truncateToDouble() and toStringAsFixed() and not use NumberFormat at all:

n.toStringAsFixed(n.truncateToDouble() == n ? 0 : 2);

So for example:

main() {
  double n1 = 15.00;
  double n2 = 15.50;

  print(format(n1));
  print(format(n2));
}

String format(double n) {
  return n.toStringAsFixed(n.truncateToDouble() == n ? 0 : 2);
}

Prints to console:

15
15.50

Upvotes: 81

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