Question

Lets supose I have a User table, and on this table I have height, weight and result rows.
In a form I input height and weight values and want to multiply those two values and store on the resulta row on database. I was trying something like that

  def create
    @user = User.new(params[:user])
    @result = @user.height * @user.weight
    @user.result = @result

But its not working, what am i doing wrong?

Answer 1

I think it would be nicer to have the computation done on a before_save filter on the model. Using the first 2 answers, it should look like this:

users_controller.rb

def create
  @user = User.new(params[:user])
  if @user.save
    redirect_to @user
  else
    render :action => :new
  end
end

user.rb

before_save :compute_result

def compute_result
  result = height * weight
end