Rails Exception Handling

Question

How can I send the error messages that are happening in the model code back to the view. I mean. I have a

begin
       Some code
rescue
       Exception Handling
end

now error occurs and in the rescue, I would like to send a message back to the controller, so that it ll get displayed in the view. Do I have to use a variable, which has to contain a number of error messages that occurs in one request, concatenate them and send it back to controller, so that I can display it in the view?. Rails already shows some error messages like field can't be blank. I am asking about the other exceptions, which occurs in the functions that are present in the model code.

Answer 1

An example of what i do in my own code:

def create
  @letter = Letter.new(params[:id])

  begin
    @letter.do_something_that_could_throw_an_exception
    flash[:notice] = I18n.translate('letter.success_create')
  rescue => e
    logger.error "letter_controller::create => exception #{e.class.name} : #{e.message}"
    flash[:error] = "#{I18n.translate('letter.letter_create_failed')}<br/>Detailed error: #{e.message}"
    ExceptionNotifier.deliver_exception_notification(e, self, request)
    # redirect somewhere sensible?
  end
end

end

Does that help?

Answer 2

Exceptions that happen as a part of saving/creating a model

I use the ActiveRecord callbacks after_validation, after_validation_on_create, and before_save (depending on the circumstance), to obtain any extra data and verify that everything is ready to be saved. Then, if any problems, I store the exception in errors[:base] using add_to_base. That way the view will display the error msg in the same way it displays any other validation errors.

Remember that if your before_save method returns false, the save will fail.

Exceptions for other model methods

All the usual methods are available:

1. Raise a specific exception that the controller will catch. The exception can include an error number that the view translates to an error msg. Or the model can export an error_num to error_msg hash
2. Return an error code as a return parameter of the method. Eg if you want to also use the Flash to give a positive msg when things work, you can return a msg_code. Then have negative msg codes for errors and positive codes for different types of success.
3. Establish an @error (or whatever) instance variable to be checked by the caller.