Dart 如何获取“值"一个枚举 [英] Dart How to get the "value" of an enum

问题描述

在 Dart 中提供枚举之前，我编写了一些繁琐且难以维护的代码来模拟枚举，现在想要简化它.我需要将枚举的值作为字符串获取，例如可以用 Java 完成但不能.

Before enums were available in Dart I wrote some cumbersome and hard to maintain code to simulate enums and now want to simplify it. I need to get the value of the enum as a string such as can be done with Java but cannot.

例如，当我想要的是MONDAY"时，小测试代码片段在每种情况下都返回day.MONDAY"

For instance little test code snippet returns 'day.MONDAY' in each case when what I want is 'MONDAY"

enum day {MONDAY, TUESDAY}
print( 'Today is $day.MONDAY');
print( 'Today is $day.MONDAY.toString()');

我是否更正了只需要解析字符串的'MONDAY'?

Am I correct that to get just 'MONDAY' I will need to parse the string?

推荐答案

遗憾的是，您认为 toString 方法返回 "day.MONDAY" 而不是更有用的 "MONDAY" 是正确的.你可以得到字符串的其余部分:

Sadly, you are correct that the toString method returns "day.MONDAY", and not the more useful "MONDAY". You can get the rest of the string as:

day theDay = day.MONDAY;      
print(theDay.toString().substring(theDay.toString().indexOf('.') + 1));

诚然，不太方便.

另一种将枚举名称作为字符串获取的方法，这种方法更短，但效率也较低，因为它也为字符串的第一部分创建了一个不必要的字符串，是:

Another way to get the enum name as a string, one which is shorter, but also less efficient because it creates an unnecessary string for first part of the string too, is:

theDay.toString().split('.').last

如果性能无关紧要，那可能就是我要写的，只是为了简洁.

If performance doesn't matter, that's probably what I'd write, just for brevity.

如果你想迭代所有的值，你可以使用day.values:

If you want to iterate all the values, you can do it using day.values:

for (day theDay in day.values) {
  print(theDay);
}

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