Where to hold select options rather then in templates?

Phoenix Forum Questions / Help
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1

Hi!

I have created a select option in my form where a User can choose his level of physical activity. It’s described in a form template.

  <%= label f, :physical_activity %>
  <%= select f, :physical_activity,
      ["Inactivity, sedentary work", 
       "Low activity, sedentary work, 1-2 workouts a week",
       "Medium activity, sedentary work, 3-4 workouts a week",
       "High activity, physical work, 3-4 workouts a week",
       "Very high activity, professional athletes, people training every day"],
      prompt: "Choose your life activity" %>
  <%= error_tag f, :physical_activity%>

I am then compering Users selected option in a model:

  def cpm_for_user(pp, user_bmr) do
      case pp.physical_activity do
        "Inactivity, sedentary work" -> user_bmr * 1.2
        "Low activity, sedentary work, 1-2 workouts a week" -> user_bmr * 1.3
        "Medium activity, sedentary work, 3-4 workouts a week" -> user_bmr * 1.5
        "High activity, physical work, 3-4 workouts a week" -> user_bmr * 1.7
        "Very high activity, professional athletes, people training every day" -> user_bmr * 1.9
      end
  end

and based on his choosing I return different result which is injected in a controller:

def show(conn, %{"id" => id}, current_user) do
   #Retriving users pp
   pp = Cpm.get_user_pp!(current_user, id)
   #Calculating users bmr
   user_bmr = Bmr.bmr_for_user(pp)
   #Calculating users cpm
   user_cpm = Bmr.cpm_for_user(pp, user_bmr)

   render(conn, "show.html", pp: pp, user_bmr: user_bmr, user_cpm: user_cpm)
 end

However, I got an information that this approach is not a good one. I should create those options somewhere else and holding them in a database is not needed. They should have corresponding integer values which I can pass around in my application and based on them, return different values.

Is there anyone who could help me come up with a solution? Thanks!

2

Check out Phoenix.HTML.Form - select/4, where it shows examples of using keyword lists for this, such as:

[
  "Inactivity, sedentary work": "1",
  "Low activity, sedentary work, 1-2 workouts a week": "2",
  "Medium activity, sedentary work, 3-4 workouts a week": "3",
  "High activity, physical work, 3-4 workouts a week": "4",
  "Very high activity, professional athletes, people training every day": "5"
]

And of course, you don’t have to include that list everywhere you use the select! Instead use:

<%= select f, :physical_activity, @activity_choices, prompt: "Choose your life activity" %>

where the assign @activity_choices is defined inside the controller. One example might be like:

def show(conn, %{"id" => id}, current_user) do
  render(conn, "show.html", activity_choices: activity_list(), other_assigns: etc...)
end

defp activity_list do
  [
    "Inactivity, sedentary work": "1",
    ...
  ]
end

EDIT: and of course, with the example above, you would change cpm_for_user/2 to use the values instead of the labels:

def cpm_for_user(pp, user_bmr) do
  case pp.physical_activity do
    "1" -> user_bmr * 1.2
    "2" -> user_bmr * 1.3
    "3" -> user_bmr * 1.5 
    "4" -> user_bmr * 1.7
    "5" -> user_bmr * 1.9
  end
end
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3

Thank you for help! This is perfect and it will help me so much with future forms! :slight_smile:

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4

I think a view is more appropriate place to keep that kind of logic(instead of controller).

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