Switch-Case Statement

🎯 Mục tiêu: Pattern matching với switch-case trong Dart 3.

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💡 Switch cổ điển

String day = "Monday";

switch (day) {
  case "Monday":
  case "Tuesday":
  case "Wednesday":
  case "Thursday":
  case "Friday":
    print("Weekday");
    break;
  case "Saturday":
  case "Sunday":
    print("Weekend");
    break;
  default:
    print("Unknown");
}

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⚡ Switch Expression (Dart 3+)

String day = "Monday";

String type = switch (day) {
  "Monday" || "Tuesday" || "Wednesday" || "Thursday" || "Friday" => "Weekday",
  "Saturday" || "Sunday" => "Weekend",
  _ => "Unknown"
};

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🎯 Pattern Matching (Dart 3+)

// Type patterns
Object value = 42;
String result = switch (value) {
  int i when i < 0 => "Negative",
  int i when i > 0 => "Positive",
  int() => "Zero",
  String s => "String: $s",
  _ => "Unknown"
};

// Record patterns
var point = (x: 10, y: 20);
var description = switch (point) {
  (x: 0, y: 0) => "Origin",
  (x: var x, y: 0) => "On x-axis at $x",
  (x: 0, y: var y) => "On y-axis at $y",
  (x: var x, y: var y) => "Point($x, $y)"
};

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📱 Trong Flutter - UI State

sealed class UiState {}
class Loading extends UiState {}
class Success extends UiState {
  final String data;
  Success(this.data);
}
class Error extends UiState {
  final String message;
  Error(this.message);
}

Widget build(BuildContext context) {
  return switch (state) {
    Loading() => CircularProgressIndicator(),
    Success(:var data) => Text(data),
    Error(:var message) => Text("Error: $message"),
  };
}

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✅ Checklist

• Dùng break trong switch cổ điển
• Dùng switch expression cho Dart 3+
• Sử dụng pattern matching với sealed classes

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