STI example

drink_habit.rb

class DrinkHabit < Habit
  # DB structure
  # id:integer
  # title:text
  # food_amount:integer
  # drink_time:datetime
  # type: string
end

food_habit.rb

class FoodHabit < Habit
  # DB structure
  # id:integer
  # title:text
  # food_amount:integer
  # drink_time:datetime
  # type: string
end

habit.rb

class Habit < ActiveRecord::Base
  # DB structure
  # id:integer
  # title:text
  # food_amount:integer
  # drink_time:datetime
  # type: string
  belongs_to :user
end

habits_controller.rb

class HabitsController < ApplicationController
  def update
    habit = Habit.find(params[:id])
    if habit.update habits_params
      redirect_to habit_path(habit)
    else
      render 'show'
    end
  end
  
  protected
  
  def habits_params
    params.require(:habit).permit(:id, :title, :food_amount, :drink_time)
  end
end

habits_slash_edit.html.erb

<%= form_for @habit do |f| %>
  <%= f.text_field :title %>
  <%= if @habit.is_a? FoodHabit %> <!-- better to use rendering of partials and helper -->
    <%= f.text_field :food_amount %>
  <% end %>
  <% if @habit.is_a? DrinkHabit %>
    <%= f.text_field :drink_time %>
  <% end %>
  <%= f.submit %>
<% end %>