如何在Ruby中使用C#样式枚举？

Question

我只想知道在Ruby中模拟C#样式枚举的最佳方法.

Answer 1

它不完全相同,但我经常会为这种事情构建一个哈希:

STATES = {:open => 1, :closed => 2, :max => 3, :min => 4}.freeze()

冻结哈希使我不会意外地修改其内容.

此外,如果您想在访问不存在的内容时引发错误,可以使用defualt Proc来执行此操作:

STATES = Hash.new { |hash, key| raise NameError, "#{key} is not allowed" }
STATES.merge!({:open => 1, :closed => 2, :max => 3, :min => 4}).freeze()

STATES[:other] # raises NameError

Answer 2

具体来说,我希望能够在给定一些变量的情况下对这组值执行逻辑测试.示例是窗口的状态:"最小化,最大化,关闭,打开"

如果你需要枚举映射到值(例如,你需要最小化等于0,最大化等于100等)我会使用符号散列值,如下所示:

WINDOW_STATES = { :minimized => 0, :maximized => 100 }.freeze

冻结(就像nate所说)会阻止你在将来意外破坏事物.这样做可以检查某些内容是否有效

WINDOW_STATES.keys.include?(window_state)

或者,如果您不需要任何值,只需要检查'membership',那么数组就可以了

WINDOW_STATES = [:minimized, :maximized].freeze

像这样使用它

WINDOW_STATES.include?(window_state)

如果您的键将成为字符串(例如RoR应用程序中的'state'字段),那么您可以使用字符串数组.我在许多rails应用程序中一直这样做.

WINDOW_STATES = %w(minimized maximized open closed).freeze

这几乎是rails validates_inclusion_of验证器专门用于:-)

个人须知:

我不喜欢打字包括？所有的时间,所以我有这个(由于.in？(1,2,3)的情况,它只是复杂的:

class Object

    # Lets us write array.include?(x) the other way round
    # Also accepts multiple args, so we can do 2.in?( 1,2,3 ) without bothering with arrays
    def in?( *args )
        # if we have 1 arg, and it is a collection, act as if it were passed as a single value, UNLESS we are an array ourselves.
        # The mismatch between checking for respond_to on the args vs checking for self.kind_of?Array is deliberate, otherwise
        # arrays of strings break and ranges don't work right
        args.length == 1 && args.first.respond_to?(:include?) && !self.kind_of?(Array) ?
            args.first.include?( self ) :
            args.include?( self )
        end
    end
end

这可以让你输入

window_state.in? WINDOW_STATES