Question

I have a create method that calls a method in a model that pings some third-party APIs.

What I need to do is if the API sends back a certain message, then I’d display an error.

Below is my current controller and model setup, so how would I get the error back in to the controller (and ultimately the view)?

Here is the method in my controller:

def create
  @number = Number.where(:tracking => params[:number][:tracking], :user_id => current_user.id).first

  if @number.blank?
    @number = Number.new
    @number.tracking = params[:number][:tracking]
    @number.user_id = current_user.id
    @number.notes = params[:number][:notes]
    @number.track
  end

  respond_with(@number) do |format|  
    format.html { redirect_to root_path }  
  end
end

Here are the methods in my model:

def track
  create_events
end


def create_events(&block)

  tracker = fedex.track(:tracking_number => number)

  if tracker.valid?    
    self.assign_tracker(tracker)

    tracker.events.each do |e|
      self.create_event(e) unless (block_given? && !block.call(e))
    end

    save
  else
    # NEED TO THROW THE ERROR HERE
  end
end

Answer 1

How about if rather than throwing errors, you just use validation? Something like the following (Just to get your started. This would need work.):

# if you don't cache the tracker in an attribute already, do this so
# you can add errors as if it were a column.
attr_accessor :tracker

def create_events(&block)

  tracker = fedex.track(:tracking_number => number)

  if tracker.valid?    
    # ...
  else
    # add the error with i18n
    errors.add(:tracker, :error_type_if_you_know_it)

    # or add it from a returned message
    errors.add(:tracker, nil, :message => fedex.get_error())
  end
end

Then in your controller:

@number.track

respond_with(@number) do |format|
  if @number.errors.any?
    format.html { redirect_to root_path }
  else
    format.html { render :some_template_with_errors }
  end
end

Alternatively you could do this as part of validation (so calling valid? would work as expected and not destroy your custom “track” errors)

# do your tracking on creation, if number was given
validate :on => :create do
  if number.present?
    tracker = fedex.track(:tracking_number => number)
    unless tracker.valid?
      errors.add :tracker, nil, :message => tracker.get_error()
    end
  end
end

# then do your actual creation of tracking events sometime after validation
before_save :handle_tracker_assignment

def handle_tracker_assignment
  self.assign_tracker(tracker)
  # note the block method you're using would need to be reworked
  # ...
end

Note in the latter case you’d have to change your logic a bit, and simply pass the tracking number and attempt to save a new record, which would trigger the tracking attempt.