Renum -- a Ruby enum gem

A while back I blogged through trying to implement something in Ruby similar to what you get from Java and C#'s enum keyword (and before there was a keyword, from the type-safe enumeration pattern in Java). It went pretty well.

I mentioned there that I might go ahead and package the thing (or something like it) up as a gem. Tonight I did. It's called Renum.

Renum lets you create enums like this:

enum :Status, [ :NOT_STARTED, :IN_PROGRESS, :COMPLETE ]

enum :Color, [ :RED, :GREEN, :BLUE ] do
  def abbr
    name[0..0]
  end
end

As of version 0.0.1, released just minutes ago, those enums work like this:

describe "enum" do
  
  it "creates a class for the value type" do
    Status.class.should == Class
  end
  
  it "makes each value an instance of the value type" do
    Status::NOT_STARTED.class.should == Status
  end
  
  it "exposes array of values" do
    Status.values.should == [Status::NOT_STARTED, Status::IN_PROGRESS, Status::COMPLETE]
  end
  
  it "enumerates over values" do
    Status.map {|s| s.name}.should == %w[NOT_STARTED IN_PROGRESS COMPLETE]
  end
  
  it "indexes values" do
    Status[2].should == Status::COMPLETE
    Color[0].should == Color::RED
  end
  
  it "provides index lookup on values" do
    Status::IN_PROGRESS.index.should == 1
    Color::GREEN.index.should == 1
  end
  
  it "allows an associated block to define instance methods" do
    Color::RED.abbr.should == "R"
  end
  
  it "provides a reasonable to_s for values" do
    Status::NOT_STARTED.to_s.should == "Status::NOT_STARTED"
  end
  
end

Hopefully someone will find this useful. There are some obvious features to add, like value lookup by name. There are also a lot of things that could be locked down a little, but the library's useful without that so I'm not sure it's worthwhile. (For example, I don't currently prevent you calling Color.new 'HAZEL'.)

If this is something you might use, let me know what you want out of it.

Also, tonight I arrived in Charlotte for RubyConf. Say hi if you see me.