Truncate to 2 decimal places without rounding - dart

Question

Can't find or work out a solution to this that works with Dart.
I've already tried:
1. toStringAsFixed() - this rounds
2. double.parse(number.toStringAsFixed()) - this rounds
3. num - num % 0.01 - this rounds
I've found some solutions on SO but they either use functions that aren't available on Flutter/Dart or didn't work for me.
Any help would be greatly appreciated.

Answer 1

To build on #Irn beautiful Answer.
The function below lets you specify how many fractional digits / how many decimal places you want
double truncateToDecimalPlaces(num value, int fractionalDigits) => (value * pow(10,
fractionalDigits)).truncate() / pow(10, fractionalDigits);
Example
truncateToDecimalPlace(4321.92385678, 3) // 4321.923
Or my favorite way is to use Dart extensions
extension TruncateDoubles on double {
double truncateToDecimalPlaces(int fractionalDigits) => (this * pow(10,
fractionalDigits)).truncate() / pow(10, fractionalDigits);
}
This lets you call the function on a double object like thus
Usage
4321.92385678.truncateToDecimalPlaces(3); // 4321.923

Answer 2

Try
double truncateToHundreths(num value) => (value * 100).truncate() / 100;
There will be cases where you lose precision, but that requires you to use almost all 53 bits of double precision in the number (when multiplying by 100 loses precision to begin with).
Going trough strings is a significant overhead that I would avoid if possible, unless you actually expect to convert the number to a string anyway afterwards.

Answer 3

(value * 100).truncateToDouble() / 100
Example:
var lat = 29.4562
lat * 100 = 2945.62
2945.62 truncateToDouble() = 2945
2945 / 100 = 29.45

Answer 4

I have used the below method
String toFixed(double value, [int decimalPlace = 1]) {
try {
String originalNumber = value.toString();
List<String> formattedNumber = originalNumber.split('.');
return "${formattedNumber[0]}.${formattedNumber[1].substring(0, decimalPlace)}";
} catch (_) {}
return value.toString();
}