CODEWITHSUNDEEP
ruby-on-rails
user1854802
user1854802

Reputation: 388

How to update table row from values determined within controller

ruby_on_rails rails 4 assignment non-screen data to insert record

Rather than using screen values (e.g. simple_form_for @user_evaluation_result) to populate the columns to insert a row I need to calculate some of the values in controller. For example if I have these statements in the controller

….
# which if I had simple_form_for user_evaluation_result would get populated by the screen 
@user_evaluation_result = UserEvaluationResult.new(user_evaluation_result_params)
….
# standard stuff I use for screen derived updates
def user_evaluation_result_params
    params.require(:user_evaluation_result).
        permit(:evaluation_assumption_id,
               :company_listing_id,
               :target_share_price_dollars )
  end

How do I assign values to :user_assumption_id etc so that insert works. I have tried all sorts of statements. Alternatively do I use another format instead of calling "def user_evaluation_result_params". Thanks in advance - Pierre

Upvotes: 0

Views: 326

Answers (1)

pdobb
pdobb

Reputation: 18037

I'm hoping I've interpreted the question properly...

First, to make sure we're on the same page... The code inside of your user_evaluation_result_params method is using Strong Parameters to create an ActionController::Parameters object for the purpose of protecting your model from unpermitted mass-assignments. So, in general, when you're creating or updating an ActiveRecord object from a form in a view template, you want to use Strong Parameters so that users can't manipulate your form to set attributes that you're not expecting.

That said, if you want to set attributes on an object you don't have to use mass assignment. Here is an example of using one-at-a-time assignment (the opposite of mass-assignment):

obj = MyObject.new
obj.attr_one = "One"
obj.attr_two = "Two"
obj.save

There is nothing wrong with this approach other than that it's kind of a lot of work for the general case. So mass-assignment just saves us from having to do this all the time. But it sounds like this one-at-a-time assignment is what you're wanting in this case. So try something like this:

def create
  @user_evaluation_result = UserEvaluationResult.new
  # assuming you have a UserAssumption object instance in `my_user_assumption`
  @user_evaluation_result.user_assumption = my_user_assumption
  @user_evaluation_result.some_other_attr = "some value"
  @user_evaluation_result.save
end

Note, instead of setting @user_evaluation_result.user_assumption_id directly, as you asked about, it is preferred to set the actual object association as I did above. Try to keep associations outside of mass-assignment and use object relationships to build up your object graphs.

Or, if you have some attributes coming from a form you can mix and match the two approaches:

def create
  @user_evaluation_result = UserEvaluationResult.new(user_evaluation_result_params)
  # assuming you have a UserAssumption object instance in `my_user_assumption`
  @user_evaluation_result.user_assumption = my_user_assumption
  @user_evaluation_result.some_other_attr = params[:user_evaluation_result][:some_other_attr]
  @user_evaluation_result.save
end

private

def user_evaluation_result_params
  params.require(:user_evaluation_result)
        .permit(:evaluation_assumption_id,
                :company_listing_id,
                :target_share_price_dollars)
end

Upvotes: 1

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