trying to add a field to an activerecord model to set some values at run time.

model and controller

# ----------------------
class MyObj < ActiveRecord::Base
  attr_accessor :i_can_select 
end

# ----------------------
class MyController < ApplicationController

  def index
    @list = MyObj.all
    
    # loop through all records and set the non persisted field to a value
    # the value is set based on the list item properties and the current user
    @list.each do |l|
      l.i_can_select = complex_routine_to_set_selectability(current_user)
    end
  end
end

----------------------
index.html.erb.....
<% @list.each do |i| %>

  <% if i.i_can_select %>
    show a cool button here for a feature when it's true!
  <% end %>
<% end %>