toPercentageText method
Example:
String number = null.toPercentageText();
print(number); // Output: 0
number = 15.toPercentageText();
print(number); // Output: 150%
number = 0.15.toPercentageText();
print(number); // Output: 15%
Implementation
String toPercentageText([
String sign = "%",
]) {
num x = this ?? 0;
if (x is double) x = x * 100;
return "${x.toInt()}$sign";
}