Combining virtual attributes to single class attributes in super class (STI) - ruby-on-rails

Question

I'm trying to combine start_date, start hour, and start_minute virtual attributes from my Event form, in order to create a start_datetime attribute (which is stored in the database).
I have (via STI) several subclasses of Event; let's call them TrainingSession and WorkSession and PersonalTime.
Classes are structured as such:
class Event < ActiveRecord::Base
...
end
class TrainingSession < Event
...
end
class WorkSession < Event
...
end
class PersonalTime < Event
...
end
The relevant parts of event.rb:
class Event < ActiveRecord::Base
attr_accessor :start_date, :start_hour, :start_minute
validates :start_datetime, :presence => true
before_validation :merge_attributes_for_datetime_string
def merge_attributes_for_datetime_string
start_datetime_string = "#{ start_date } #{ start_hour }:#{ start_minute }:00"
end
def start_datetime=(start_datetime_string)
self.start_datetime = start_datetime_string
end
def start_date
start_datetime.strftime("%d") if start_datetime?
end
def start_hour
start_datetime.strftime("%H") if start_datetime?
end
def start_minute
start_datetime.strftime("%M") if start_datetime?
end
end
... and of events_controller.rb:
def create
#event = Event.new(event_params)
if #event.save
redirect_to :root, :flash => { :success => "Event added." }
else
redirect_to :back, :flash => { :notice => "There was an error creating the event." }
end
end
private
def event_params
params.require(:event).permit(
:type,
:start_datetime,
:start_date,
:start_hour,
:start_minute,
...
)
end
def training_session_params
params.require(:training_session).permit(
...
)
end
def work_session_params
params.require(:work_session).permit(
...
)
end
def personal_time_params
params.require(:personal_time).permit(
...
)
end
I've verified in my server logs that the correct params are being sent from the form:
Parameters: {"utf8"=>"✓", "authenticity_token"=>"<TOKEN HERE>=", "event"=>{"start_date" => "2013-08-23", "start_hour"=>"15", "start_minute"=>"00", "type"=>"PersonalTime"}, "commit"=>"Add Personal Time"}
Yet every time I try to create an Event (of any type), I get the notice There was an error creating the event. (as per my create method). If I comment out validates :start_datetime, the event is created, but with start_datetime of nil.
This has to mean the start_datetime string isn't being properly merged from the virtual attributes, but I can't figure out why.
What am I missing here? Is there a better way to set start_datetime?

Answer 1

Based on what you've posted, I don't see where you are calling the start_datetime method.
Instead of defining a new method, you could do the merging in your start_datetime method as follows:
before_validation :merge_attributes_for_datetime_string
def merge_attributes_for_datetime_string
self.start_datetime = "#{ start_date } #{ start_hour }:#{ start_minute }:00"
end