validation help please

Hi,

Can anyone take a look at this.... i've been banging my head on the
wall for several days trying to figure this out. I can't figure out why
the validation is bypassed. The only clue I have is it seems its not
evaluating :question_type == "standard" to true.

Model:
validates :question_type, :presence => true
    if :question_type == "standard"
      validates :question, :presence => true
    ...

Controller:
def create
    @question = Question.new(params[:question])
  if @question.save
          if params[:question_type] == "standard"
            flash[:success] = "Question created!"
            redirect_to @question
          else
            .....

new.html.erb:
<%= f.submit 'Save', question_type: "standard" ...

Is that code just inline in the model? If so then it is only executed
once, when the code is loaded, so the if statement is not tested for
each object being validated. Have a look at the Rails Guide on
ActiveRecord Validations and Callbacks to see ways that you can
accomplish what you want.

Colin

Hi Dave,

I believe you should do something along the lines of

Model:

  validates_each :question do |record, attr, value|
    record.errors.add attr, 'The question is not present!?' if value.blank? and record.question_type=="standard"
  end

plz correct me if I'm wrong, Colin :slight_smile:

cheers,
Walther

Hi Dave,

I believe you should do something along the lines of

Model:

        validates_each :question do |record, attr, value|
                record.errors.add attr, 'The question is not present!?' if value.blank? and record.question_type=="standard"
        end

plz correct me if I'm wrong, Colin :slight_smile:

It might be easier to use :if

Colin

This code is evaluated when the model is loaded. It compares the symbol :question_type to the string ‘standard’ (which are of course never equal) and so doesn’t add the validation.

You want the choice of whether to apply the validation or not to be taken when the model is about to be validated. The standard way of doing that is with the :if option

validates :question_type, :presence => true
validates :question, :presence => true, :if => :standard_question?

will call the standard_question? method and only enforce the presence validation on question if the method returns true. There is also a lambda form

validates :question, :presence => true, :if => lambda {|record| record.question_type == ‘standard’}

Fred

Ok,

Thank you. I read Rails Guide on ActiveRecord Validations and
Callbacks, specifically Conditional Validation.

So,
validates :question, :presence => true, :if => "question_type.blank?"
placed inline in model should be the simplest way to do this. It does
not work however. My lack of understanding seems to be related to how I
specify question_type in the condition?

As you can see i'm still on the bottom of the steep part of the learning
curve.'

Thanks for the help

Frederick Cheung wrote in post #1099720:

Lambda method works, although I don't understand it :slight_smile:

Thanks!!

Dave

Yes - it’s up to you to write a standard_question? method. The lambda saves you having to have the condition in a separate method but can make your validation look more cluttered (especially for more complicated conditions).

Fred

Thanks again,

Is there a way to add a message if validation fails using lambda method
(I am using Lambda method until I can figure out why
validates :question, :presence => true, :if
=>:standard_question?
generates
undefined method `standard_question?' for #<Question:0x007f947ddb2e00>)

Dave, you have to add an instance method “standard_question?” to your model

def standard_question?

end

from the url below you can see that you can pass a :message param to customize the error message

http://guides.rubyonrails.org/active_record_validations_callbacks.html#message

You want the choice of whether to apply the validation or not to be
taken when the model is about to be validated.
http://www.hqew.net