Rust Enums compared to Ruby objects

So far we’ve discussed Strings and Numbers which are relatively comparable in Rust and Ruby. At least both languages have those concepts as first-class citizens. In this post, we are going to discuss Enums.

Photo by Irham Setyaki on Unsplash

If you are coming from Ruby, you may not be completely familiar. More than likely you’ve heard of Enums in the context of database validation. Typically, we’d use Enums while deciding if a given value is an acceptable value for a database column. In Ruby, a lot of times this is done using a list of acceptable values.

In our project files from the previous posts, we’ll create types of users. The types will be used to illustrate the use of Rust Enums.

In Ruby, we could do something like this:

class Admin
   NAME = "Administrator"
end

class NonAdmin
   NAME = "Application User"
end

class User
   USER_KINDS = [Admin, NonAdmin]
   attr_accessor :kind

   def self.admin
      USER_KINDS.first
   end

   def self.nonadmin
      USER_KINDS.last
   end
end

my_user = User.new
my_user.kind = User.admin # we could have used USER_KINDS.first

puts my_user.kind # prints out Admin
puts my_user.kind::NAME # prints out Administrator

We could add validation to this to make sure that User#kind is only ever set to a value included in USER_KINDS constant, but let’s see what the equivalent is in…