ruby on rails - Calculation in model or controller -

i'm builing weight loss app. in app each user has_one :profile , has_many :weights. each profile belongs_to :pal. app work need value called smr formula takes variables user's size, age , gender (all profiles table), user's current weight (from weights table) float number pal table.

i able calculate smr in profiles_controller.rb show action , show in profiles show.html.erb.

i have 2 questions now:

1. is correct calculation in profiles_controller.rb show action or should in profile.rb model? if should in model: how can (how should code like)?
2. i need smr value later on in app variable other calculations well. how can achieve (if calculated in profile controller/model needed somewhere else later on)?

i'm new rails world maybe questions noob questions.

profile.rb

class profile < activerecord::base   belongs_to :user   belongs_to :pal   belongs_to :goal     def age     if birthdate != nil       = time.now.utc.to_date       now.year - birthdate.year - (birthdate.to_date.change(:year => now.year) > ? 1 : 0)     else       nil     end   end end  

weight.rb

class weight < activerecord::base   belongs_to :user end 

pal.rb

class pal < activerecord::base   has_many :profiles end 

profiles_controller.rb (show action only)

  def show     @pal = @profile.pal     @goal = @profile.goal     @current_weight = weight.where(:user_id => current_user.id).order(:day).last      if @profile.gender == 0       @smr = (10*@current_weight.kilograms+6.25*@profile.size-5*@profile.age+5)*@pal.value     elsif @profile.gender == 1       @smr = (10*@current_weight.kilograms+6.25*@profile.size-5*@profile.age-161)*@pal.value     else       nil     end   end 

i think should create separate class or can on profile model well

class smrcalculator   def initialize(profile, user)      @profile = profile      @user = user   end    def get_smr     @pal = @profile.pal     @goal = @profile.goal     @current_weight = weight.where(:user_id => @user.id).order(:day).last      if @profile.gender == 0       @smr = (10*@current_weight.kilograms+6.25*@profile.size-5*@profile.age+5)*@pal.value     elsif @profile.gender == 1       @smr = (10*@current_weight.kilograms+6.25*@profile.size-5*@profile.age-161)*@pal.value     else       nil     end   @smr   end  end 

and call class on controller show method this:

@smr_calculator = smrcalculator.new(@profile, current_user) @smr = @smr_calculator.get_smr 

and add class smr_calculator.rb in models folder

so anywhere in app need @smr can call class profile , current user