start

Author: yinhuasheng

start/main.dart

@@ -1,3 +1,187 @@
+import 'dart:ffi';
+import 'dart:io';
+
 void main() {
   print('Hello World');
 }
+
+var name = "Tom";
+var year = 2024;
+var temp = 31.3;
+var languages = ["C", "C#", "Go", "Dart"];
+var person = {
+  'name': "Lee",
+  'age': 18,
+  'hobby': ['eat', 'sleep']
+};
+
+bool odd(int number) {
+  if (number % 2 == 0) {
+    return false;
+  } else {
+    return true;
+  }
+}
+
+void loop(int count) {
+  for (int i = 0; i < count; i++) {
+    print("i");
+  }
+
+  var hobbies = ["eat", "sleep", "play"];
+  for (var hobby in hobbies) {
+    print(hobby);
+  }
+}
+
+int fib(int n) {
+  if (n == 0 || n == 1) {
+    return n;
+  }
+  return fib(n - 1) + fib(n - 2);
+}
+
+var result = fib(10);
+
+void func() {
+  var hobbies = ["eat", "sleep", "play"];
+  hobbies.where((hobby) => hobby.endsWith("t")).forEach(print);
+}
+
+class Spacecraft {
+  String name;
+  DateTime? time;
+
+  //这是一个getter方法
+  int? get timeYear => time?.year;
+
+  //构造函数
+  Spacecraft(this.name, this.time) {}
+
+  //这也是构造函数
+  Spacecraft.noTime(String name) : this(name, null);
+
+  void describe() {
+    //这是我见过最简单的模板字符串 既没有要求是特殊的引号封装，也没有要求${}写法
+    print("Spacecraft:$name");
+    var time = this.time;
+    if (time != null) {
+      int years = DateTime.now().difference(time).inDays ~/ 365;
+      print('Launched: $time ($years years ago)');
+    } else {
+      print("no time");
+    }
+  }
+}
+
+var voyager = Spacecraft('Voyager', DateTime(2000, 1, 1));
+
+var voyager2 = Spacecraft.noTime('Voyager2');
+
+//枚举
+enum Status { INIT, SUCCESS, FAIL, DEATH }
+
+//增强枚举
+enum Os {
+  Win(name: "Windows", year: 1998),
+  Mac(name: "Mac", year: 1997),
+  Linux(name: "Linux", year: 2002);
+
+  final String name;
+  final int year;
+
+  const Os({required this.name, required this.year});
+
+  bool get isWin => this == Os.Win;
+}
+
+var win10 = Os.Win;
+
+//扩展类
+class Orbiter extends Spacecraft {
+  double altitude;
+  Orbiter(super.name, super.time, this.altitude);
+
+  @override
+  void describe() {
+    print("this is Orbiter and altitude is $altitude");
+    super.describe();
+  }
+}
+
+mixin Piloted {
+  int astronauts = 1;
+
+  void describeCrew() {
+    print('Number of astronauts: $astronauts');
+  }
+}
+
+//mixin-with 可以让一个类获得增强 但mixin中的成员不属于this
+class PilotedCraft extends Spacecraft with Piloted {
+  PilotedCraft(super.name, super.time);
+
+  void say() {
+    print(astronauts);
+    describeCrew();
+  }
+}
+
+//所有的类都隐式定义成了一个接口。因此，任意类都可以作为接口被实现
+class MockSpaceship implements Spacecraft {
+  @override
+  String name;
+
+  @override
+  DateTime? time;
+
+  @override
+  void describe() {
+    // TODO: implement describe
+  }
+
+  @override
+  // TODO: implement timeYear
+  int? get timeYear => throw UnimplementedError();
+
+  MockSpaceship(this.name);
+}
+
+abstract class Person {
+  void sayHello();
+  void sayBye() {
+    print("bye");
+  }
+}
+
+//async await
+const oneSecond = Duration(seconds: 1);
+
+Future<void> printWithDelay(String message) {
+  return Future.delayed(oneSecond).then((_) {
+    print(message);
+  });
+}
+
+Future<void> printWithDelayAwait(String message) async {
+  await Future.delayed(oneSecond);
+  print("message");
+}
+
+Future<void> createDescriptions(Iterable<String> fileNames) async {
+  for (final fileName in fileNames) {
+    try {
+      var file = File(fileName);
+      if (await file.exists()) {
+        var modified = await file.lastModified();
+        print(
+            'File for $fileName already exists. It was modified on $modified');
+      } else {
+        await file.create();
+        await file.writeAsString("create File $fileName");
+      }
+    } on IOException catch (e) {
+      print("create file $fileName exception:$e");
+    }
+  }
+}