Question

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.

Answer 1

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