SwiftyEnum

gem 'swifty_enum'

# Define enum class.
class Flag

  # Required: Include SwiftyEnum module.
  include SwiftyEnum

  # Now you can define enum case by 'def_case' statement.
  #   Usage: def_case CASE_NAME [RAWVALUE]
  def_case :On, '1'
  def_case :Off, '0'

  # You can define method for each enum cases by 'def_method' statement.
  # Please put this statement below all of 'def_case' statements.
  #   Usage: def_method METHOD_NAME { || ... }
  def_method :status do |enum_case|
    case enum_case
    when On then
      # You can't use return statement, but value of last statement is returned from enum method.
      'OK'
    when Off then
      'NG'
    end
  end
end


# Enum case is defined as subclass.
Flag::On                       # => Flag::On

# Enum case has class method 'hashvalue'.
# It is incremental value by enum case definition.
Flag::On.hashvalue             # => 0

# Enum case has class method 'rawvalue'.
# If rawvalue is not given in definition, hashvalue is used instead.
Flag::On.rawvalue              # => '1'

# Enum case can be gotten by 'get' method with rawvalue.
Flag.get('1')                  # => Flag::On
Flag.get('0')                  # => Flag::Off

# If invalid rawvalue is given, 'get' method returns nil.
Flag.get('2')                  # => nil

# Enum case can be handled with case-when statement.
on = Flag.get('1')
case on
when Flag::Off then
  puts 'NG'
when Flag::On then
  puts 'OK'
else
  puts 'NG'
end
# >> OK

# Enum method is defined in each enum cases.
Flag::On.status                # => 'OK'
Flag::Off.status               # => 'NG'

# Arguments of enum method can be handled as variable arguments.
class Flag
  def_method :status_with do |enum_case, args|
    if args.empty?
      enum_case.status
    else
      with = args.join(', ')
      "#{enum_case.status} with #{with}"
    end
  end
end
Flag::On.status_with('foo')    # => 'OK with foo'

# When you want to get all of enum cases, use 'enum_cases'.
Flag.enum_cases                # => [Flag::On, Flag::Off]