truth function
Implementation
bool truth(dynamic v) {
if (v == null) {
return false;
} else if (v is bool) {
return v;
} else if (v is num) {
return v != 0;
} else if (v is String) {
return v.isNotEmpty;
} else if (v is List || v is Map) {
return v.isNotEmpty;
}
return true;
}