How do i specify and validate an enum in rails?

I currently have a model Attend that will have a status column, and this status column will only have a few values for it. STATUS_OPTIONS = {:yes, :no, :maybe}

1) I am not sure how i can validate this before a user inserts an Attend? Basically an enum in java but how could i do this in rails?

Now that Rails 4.1 includes enums you can do the following:

class Attend < ActiveRecord::Base
    enum size: [:yes, :no, :maybe]
    # also can use the %i() syntax for an array of symbols:
    # %i(yes no maybe)
    validates :size, inclusion: { in: sizes.keys }
end

Which then provides you with a scope (ie: Attend.yes, Attend.no, Attend.maybe for each a checker method to see if certain status is set (ie: #yes?, #no?, #maybe?), along with attribute setter methods (ie: #yes!, #no!, #maybe!).

Rails Docs on enums

Create a globally accessible array of the options you want, then validate the value of your status column:

class Attend < ActiveRecord::Base

  STATUS_OPTIONS = %w(yes no maybe)

  validates :status, :inclusion => {:in => STATUS_OPTIONS}

end

You could then access the possible statuses via Attend::STATUS_OPTIONS