Rails creating a collection without an association - sql

Question

What is the best and correct way to setup a simple_forms_for field that contains a collection for a select field but the values to be contained in the select need to be sourced from a model that does not have a direct association to the calling fields model?
For example I have a simple_forms_for form like follows:
<%= simple_form_for(#customer) do |f| %>
<%= f.error_notification %>
<fieldset>
<div class="form-inputs">
<%= f.input :code, required: true %>
<%= f.input :name, required: true %>
<%= f.input :location, required: true %>
<%= f.input :service_level %>
<%= f.input :golive_date, :as => :date_picker %>
<%= f.input :connection_type %>
<%= f.input :service_centre %>
<%= f.input :end_date, :as => :date_picker %>
<%= f.input :sla %>
<%= f.input :project_code %>
</div>
<div class="form-actions">
<%= f.button :submit, :class => "btn btn-primary" %>
</div>
</fieldset>
<% end %>
I want to make the :service_level field a selection field and add a collection to it, however the table that stores the lookup values is not associated with the Customer table for the form.
class Lookup < ActiveRecord::Base
validates_presence_of :name, :description
has_many :lookup_values
accepts_nested_attributes_for :lookup_values, :reject_if => lambda { |a| a[:content].blank? }, :allow_destroy => true
end
class LookupValue < ActiveRecord::Base
belongs_to :lookup
end
class CreateLookups < ActiveRecord::Migration
def change
create_table :lookups do |t|
t.string :name
t.string :description
t.timestamps
end
end
end
class CreateLookupValues < ActiveRecord::Migration
def change
create_table :lookup_values do |t|
t.integer :lookup_id
t.string :name
t.string :value
t.timestamps
end
end
end
I basically want to be able to populate the values of the select using the following SQL query:
select v.name||' - '||v.value
from lookup_values v,
lookups l
where v.lookup_id = l.id
and l.name = 'Service level';
The actual value that is saved into the :service_level field needs to be the value of v.name.
All of the collections examples I have seen only appear to show how to create selects based on models that have an association between them, just wondering if there is an easy way to achieve this without an association.

Answer 1

Ok, well this is embarrassing...
Simple solution was to modify the _form.html.erb view file so that the :service_level field reads as:
<%= f.input :service_level, :collection => LookupValue.joins(:lookup).where(lookups: { :name => 'Service level' }).pluck(:name) %>
I probably need to make this more DRY when repeating for multiple lookup values in the form.
Any ideas how I can enhance this code to:
Remove the blank value that is listed in the select field drop down?
Modify the value text that displays in the select drop down to be
Name ||' - '||value. For example show the values in the format
"L1 - Level 1". The actual value selected and saved would need to
remain as "L1" (the :name value)