How to Add an Error Message when using a Virtual Attribute - ruby-on-rails

Question

I have a date field that is not a required field. I am using Chronic to format the user input string to a valid rails format for a date field. If Chronic is unable to parse the date, I would like to raise an error, rendering the edit view with the respective error message and the originally input value. Currently the update is successful if an invalid date is entered but nothing is updated for the service_date field.
new.html.erb
<%= f.text_field :service_date_text %>
bill.rb
require 'chronic'
class Bill < ActiveRecord::Base
def service_date_text
service_date.try(:strftime, "%m/%d/%Y")
end
def service_date_text=(date)
if date.present?
if Chronic.parse(date)
self.service_date = Chronic.parse(date)
else
self.errors.add(:service_date_text, "invalid date format hello.")
end
else
self.service_date = ''
end
end
end
bills_controller.rb
def update
#bill = current_account.bills.find(params[:id])
if #bill.update_attributes(bill_params)
redirect_to #bill, notice: 'Bill has been successfully updated.'
else
render :edit
end
end
private
def bill_params
params.require(:bill).permit(:description, :notes, :po_number, :service_date_text)
end

Answer 1

errors is cleared whenever you run valid?, which update_attributes does.
Example:
irb(main):001:0> album = Album.new
=> #<Album id: nil, name: nil, release_date: nil, rating: nil, genre_id: nil,
artist_id: nil, created_at: nil, updated_at: nil>
irb(main):004:0> album.errors.add :artist, "You've selected Justin Bieber (!!!)"
=> ["You've selected Justin Bieber (!!!)"]
irb(main):006:0> album.errors.messages
=> {:artist=>["You've selected Justin Bieber (!!!)"]}
irb(main):007:0> album.valid?
=> true
irb(main):008:0> album.errors.messages
=> {}
Don't abuse setters, use proper validations. For example (not tested):
require 'chronic'
class Bill < ActiveRecord::Base
validate :service_date_validation
def service_date_text
service_date.try(:strftime, "%m/%d/%Y")
end
def service_date_text=(date)
if date.present?
if Chronic.parse(date)
self.service_date = Chronic.parse(date)
else
self.service_date = false
end
else
self.service_date = ''
end
end
private
def service_date_validation
if self.service_date == false
self.errors.add(:service_date_text, "invalid date format hello.")
end
end
end
... There are also some gems which provide date validations, such as:
https://rubygems.org/gems/validates_timeliness
https://rubygems.org/gems/date_validator
https://rubygems.org/gems/rails_validations (disclaimer: I am the author)
... as well as some others...

Answer 2

I'll bet the issue is that Rails doesn't expect setter methods to add errors. I would make service_date_text just an attr_accessor and then call a validate method which sets service_date or adds an error.
attr_accessor :service_date_text
validate :service_date_text_format
private
def service_date_text_format
return unless service_date_text # or self.service_date ||= '' and then return
if date = Chronic.parse(date)
self.service_date = date
else
errors.add(:service_date, 'invalid format')
end
end