rubyenums

How to implement Enums in Ruby?

What's the best way to implement the enum idiom in Ruby? I'm looking for something which I can use (almost) like the Java/C# enums.

Solution

  • Two ways. Symbols (:foo notation) or constants (FOO notation).

    Symbols are appropriate when you want to enhance readability without littering code with literal strings.

    postal_code[:minnesota] = "MN"
postal_code[:new_york] = "NY"

    Constants are appropriate when you have an underlying value that is important. Just declare a module to hold your constants and then declare the constants within that.

    module Foo
  BAR = 1
  BAZ = 2
  BIZ = 4
end
 
flags = Foo::BAR | Foo::BAZ # flags = 3

    Added 2021-01-17

    If you are passing the enum value around (for example, storing it in a database) and you need to be able to translate the value back into the symbol, there's a mashup of both approaches

    COMMODITY_TYPE = {
  currency: 1,
  investment: 2,
}

def commodity_type_string(value)
  COMMODITY_TYPE.key(value)
end

COMMODITY_TYPE[:currency]

    This approach inspired by andrew-grimm's answer https://stackoverflow.com/a/5332950/13468

    I'd also recommend reading through the rest of the answers here since there are a lot of ways to solve this and it really boils down to what it is about the other language's enum that you care about