Type Conversion trong Dart

// Safe parsing (returns null if failed)
int? a = int.tryParse("123");     // 123
int? b = int.tryParse("abc");     // null
double? c = double.tryParse("3.14"); // 3.14
 
// Với default value
int age = int.tryParse(input) ?? 0;

// Number → String
String s = 42.toString();       // "42"
String d = 3.14159.toStringAsFixed(2);  // "3.14"
 
// int ↔ double
int i = 3.14.toInt();          // 3
double d = 42.toDouble();      // 42.0
int r = 3.14.round();          // 3

// is - type check
if (value is String) {
  print(value.length);  // Auto-cast
}
 
// as - explicit cast
String s = obj as String;
String? s2 = obj as String?;  // Nullable cast