Created
March 14, 2024 08:14
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class Spacecraft { | |
// プロパティ | |
String name; | |
DateTime? launchDate; | |
// 読み込み専用プロパティのgetter | |
int? get launchYear => launchDate?.year; | |
// コンストラクタ。`this.`の糖衣構文によって引数をメンバに代入しています | |
Spacecraft(this.name, this.launchDate) { | |
// コンストラクタで初期するコードを記述します | |
} | |
// 名前付きコンストラクタ。`this(name, null)`はデフォルトコンストラクタを呼び出します。 | |
Spacecraft.unlaunched(String name) : this(name, null); | |
// メソッド | |
void describe() { | |
// '$name'は文字列補完によって変数の内容を文字列に変換しています。 | |
print('Spacecraft: $name'); | |
var launchDate = this.launchDate; | |
if (launchDate != null) { | |
int years = DateTime.now().difference(launchDate).inDays ~/ 365; | |
print('Launched: $launchYear ($years years ago)'); | |
} else { | |
print('Unlaunched'); | |
} | |
} | |
} | |
void main() { | |
var voyager = Spacecraft('Voyager I', DateTime(1977, 9, 5)); | |
voyager.describe(); | |
var voyager3 = Spacecraft.unlaunched('Voyager III'); | |
voyager3.describe(); | |
} |
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