Dart是否支持枚举？ [英] Does Dart support enumerations?

问题描述

Dart支持枚举吗？例如：

Does Dart support enumerations? For instance:

enum myFruitEnum { Apple, Banana }

对文档进行粗略搜索表明没有。

A cursory search of the docs suggests no.

推荐答案

href =http://news.dartlang.org/2014/11/dart-18-library-improvements-and.html =noreferrer> 1.8 ，您可以使用如下的枚举：

Beginning 1.8, you can use enums like this:

enum Fruit {
  apple, banana
}

main() {
  var a = Fruit.apple;
  switch (a) {
    case Fruit.apple:
      print('it is an apple');
      break;
  }

  // get all the values of the enums
  for (List<Fruit> value in Fruit.values) {
    print(value);
  }

  // get the second value
  print(Fruit.values[1]);
}

---

：

---

The old approach before 1.8:

class Fruit {
  static const APPLE = const Fruit._(0);
  static const BANANA = const Fruit._(1);

  static get values => [APPLE, BANANA];

  final int value;

  const Fruit._(this.value);
}

类中的静态常量是编译时常量，用于 switch 语句：

Those static constants within the class are compile time constants, and this class can now be used in, for example, switch statements:

var a = Fruit.APPLE;
switch (a) {
  case Fruit.APPLE:
    print('Yes!');
    break;
}

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