How remove leading 0 in a string - dart

Question

I get Ids in a String format that contain leading zeroes. I would like to keep this String format but without the leading zeroes. Example:
00 => 0
01 => 1
02 => 2
10 => 10
11 => 11
My current implementation is
String id = int.parse(originalId).toString()
Is there a better / efficient / Dart pattern way to achieve this conversion ?

Answer 1

You could use RegExp which may be uglier but faster than double conversion :
"01".replaceAll(new RegExp(r'^0+(?=.)'), '')
´^´ matches the begining of the string
0+ matches one or more 0 character
(=?.) matches a group (()) of any characters except line breaks (.) without including it in the result (=?), this ensures that not the entire string will be matched so that we keep at least one zero if there are only zeroes.
Example :
void main() {
final List nums = ["00", "01", "02", "10", "11"];
final RegExp regexp = new RegExp(r'^0+(?=.)');
for (String s in nums) {
print("$s => ${s.replaceAll(regexp, '')}");
}
}
Result :
00 => 0
01 => 1
02 => 2
10 => 10
11 => 11
EDIT : Performance test thanks to your comment
void main() {
Stopwatch stopwatch = Stopwatch()..start();
final RegExp reg = RegExp(r'^0+(?=.)');
for (int i = 0; i < 20000000; i++) {
'05'.replaceAll(reg, '');
}
print('RegExp executed in ${stopwatch.elapsed}');
stopwatch = Stopwatch()..start();
for (int i = 0; i < 20000000; i++) {
int.parse('05').toString();
}
print('Double conversion executed in ${stopwatch.elapsed}');
}
Result :
RegExp executed in 0:00:02.912000
Double conversion executed in 0:00:03.216000
The more operations you will do the more it will be efficient compared to double conversion. However RegExp may be slower in a single computation because creating it has a cost, but we speak about a few microseconds... I would say that unless you have tens of thousands of operations just use the more convenient to you.

Answer 2

If anyone is trying to prevent leading zeros in a TextField, I made a TextInputFormatter that will remove all leading zeros once a non-zero number is added.
class NoLeadingZeros extends TextInputFormatter {
#override
TextEditingValue formatEditUpdate(
TextEditingValue oldValue,
TextEditingValue newValue,
) {
if (newValue.text.startsWith('0') && newValue.text.length > 1) {
return TextEditingValue().copyWith(
text: newValue.text.replaceAll(new RegExp(r'^0+(?=.)'), ''),
selection: newValue.selection.copyWith(
baseOffset: newValue.text.length - 1,
extentOffset: newValue.text.length - 1,
),
);
} else {
return newValue;
}
}
}
The tricky part is adjusting the TextSelection offsets once the zeros are removed. Without this update, the TextField will stop working.

Answer 3

I think you have the most elegant form already! There options for toStringAsFixed (https://api.dart.dev/stable/1.19.1/dart-core/num/toStringAsFixed.html, mostly floating points) and NumberFormat (https://pub.dev/documentation/intl/latest/intl/NumberFormat-class.html), but I feel these might not cover your case

Answer 4

If you have string value such as "01","001","0230" and If you want to remove leading zero then try this method. Worked for me.
num.parse('001').toInt() // where 001 is a string with leading zero
Thanks, Keep Learning