Literal::Enum indexes

[joeldrapper]

In this PR, I’m adding an index macro to Enum, which allows you to generate Hash indexes for O(1) lookups. The index can be generated from any attribute or Proc calculation on a member.

class Language < Literal::Enum(Integer)
  index :name, String, unique: true

  EN(0) do
    def name = "English"
  end

  FR(1) do
    def name = "French"
  end
end

Language.where(name: "English") # => [Language::EN]
Language.find_by(name: "English") # => Language::EN

You can only use find_by for unique indexes.

The indexes are generated using a Proc, which defaults to name.to_proc, however you a pass a block instead.

index :name, String, unique: true do |language|
  language.name.upcase
end

[joeldrapper]

Should extend Literal::Types here now that index accepts a type argument.

[stevegeek]

Some off the top of my head thoughts:

Could the behaviour be mixed in to subclasses as needed instead? (or maybe there is a new subclass of Enum, eg "IndexedEnum" which includes it?)

If included in base Enum could @index_definitions and @indexes hashes be created lazily, or only if indexes are defined? Though I guess the number of extra hashes created will be small given the number of Enums created in an app will prob be relatively limited

[joeldrapper]

@stevegeek Good idea. I think it probably makes sense to have this feature in the main Enum class, but the additional hashes could be created lazily.