[ACCEPTED]-Does Dart have sprintf, or does it only have interpolation?-dart

Accepted answer
Score: 11

String interpolation covers most of your 2 needs. If you want to format numbers directly, there 1 is also num.toStringAsPrecision().

Score: 6

A String.format method does not currently exists but 1 there is a bug/feature request for adding it.

Score: 6

The intl library provides several helpers 3 to format values. See the API documentation 2 at http://api.dartlang.org/docs/releases/latest/intl.html

Here is an example on how to convert 1 a number into a two character string:

import 'package:intl/intl.dart';

main() {
    var twoDigits = new NumberFormat("00", "en_US");
    print(twoDigits.format(new Duration(seconds: 8)));
}
Score: 6

I took a different approach to this issue: by 4 padding the string directly, I don't have 3 to use any libraries (mainly because the 2 intl library seems to be discontinued):

x.toString().padLeft(2, "0");

Would 1 be the equivalent of sprintf("%02d", x);

Score: 2

Here is my implementation of String.format 2 for Dart. It is not perfect but works good 1 enough for me:

static String format(String fmt,List<Object> params) {
  int matchIndex = 0;
  String replace(Match m) {
    if (matchIndex<params.length) {
      switch (m[4]) {
        case "f":
          num val = params[matchIndex++];
          String str;
          if (m[3]!=null && m[3].startsWith(".")) {
            str = val.toStringAsFixed(int.parse(m[3].substring(1)));
          } else {
            str = val.toString();
          }
          if (m[2]!=null && m[2].startsWith("0")) {
             if (val<0) {
               str = "-"+str.substring(1).padLeft(int.parse(m[2]),"0");
             } else {
               str = str.padLeft(int.parse(m[2]),"0");
             }
          }
          return str;
        case "d":
        case "x":
        case "X":
          int val = params[matchIndex++];
          String str = (m[4]=="d")?val.toString():val.toRadixString(16); 
          if (m[2]!=null && m[2].startsWith("0")) {
            if (val<0) {
              str = "-"+str.substring(1).padLeft(int.parse(m[2]),"0");
            } else {
              str = str.padLeft(int.parse(m[2]),"0");
            }
          }
          return (m[4]=="X")?str.toUpperCase():str.toLowerCase();
        case "s":
          return params[matchIndex++].toString(); 
      }
    } else {
      throw new Exception("Missing parameter for string format");
    }
    throw new Exception("Invalid format string: "+m[0].toString());
  }

Test output follows:

  format("%d", [1]) // 1
  format("%02d", [2]) // 02
  format("%.2f", [3.5]) // 3.50
  format("%08.2f", [4]) // 00004.00
  format("%s %s", ["A","B"]) // A B
  format("%x", [63]) // 3f
  format("%04x", [63]) // 003f
  format("%X", [63]) //3F
Score: 1

Yes, Dart has a sprintf package: https://pub.dev/packages/sprintf. It is 1 modeled after C's sprintf.

Score: 0

See a format package. It is similar to format() from Python. It 1 is a new package. Needs testing.

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