Rails: Raising Model Exceptions, Rescuing in Controller

Ruby
1

Consider this bit of code:


## News model
class News < ActiveRecord::Base
  before_create :validate_date
  def validate_date
    raise "Invalid creation date..."  if created_on > Time.now
  end
end

##News controller
class Publish::NewsController < Publish::BaseController
  def create
    begin
      @news = News.new(params[:news])
    rescue
      flash[:notice] = "Invalid creation date"
      render :action => 'new'
    end
    if @news.save
      flash[:notice] = 'News was successfully created.'
      redirect_to :action => 'list'
    else
      render :action => 'new'
    end
  end
end

… I’m well off here, I know. When date validation fails I see a RuntimeError in the controller and the string specified in the News.validate_date method.

Can someone explain how to properly deal with raising exceptions in the model and rescuing in the controller? Much appreciated…

2

You’re taking the right approach to rescuing exceptions however you are taking the wrong approach to your validations by using exceptions.

Rails already has a built-in mechanism for dealing with whether or not a record is a valid so instead of raising an exception what you should be doing is adding your error to the errors array. This will make @yourobject.valid? and @yourobject.save return false.

Theres also no need to set the validation method as a callback as Rails already has validation hooks you can tie into. So you should do something like this:


class News < ActiveRecord::Base
  protected
    def validate
      self.errors.add(:created_on, "is invalid") if self.created_on > Time.now
    end
end

class Publish::NewsController < Publish::BaseController
  def create
    @news = News.new(params[:news])
    if @news.save
      flash[:notice] = 'News was successfully created.'
      redirect_to :action => 'list'
    else
      flash[:error] = @news.errors
      render :action => 'new'
    end
  end
end

More information on Rails errors and validations:

http://api.rubyonrails.org/classes/ActiveRecord/Errors.html

3

Cheers thanks for that, Luke.