toIso8601String method
Implementation
String toIso8601String() {
var str = "";
if (negated) str += "-";
str += "P";
bool hasTime = false;
for (final unit in TimeSpanUnit.values) {
final section = unit.append(this);
if (section.isNotEmpty && unit.isTimeField && !hasTime) {
hasTime = true;
str += "T";
}
str += section;
}
return str;
}