Settings model for rails

create_settings.rb

class CreateSettings < ActiveRecord::Migration
  def change
    create_table :settings do |t|
      t.string :key
      t.string :human_name
      t.text :value
      t.timestamps null: false
    end
  end
end

edit.html.haml

.row
  .col-sm-7
    = simple_form_for [:admin, @setting] do |f|
      .form-group
        %h3
          = @setting.human_name
        = f.input :value, as: :text, input_html: { rows: 2 }

      .form-actions
        = f.button :submit, class: 'btn btn-primary'
        = link_to 'Back', :back, class: 'btn btn-default'

index.html.haml

%h4 Settings

%table.table.table-responsive
  %thead
    %tr
      %th Value
      %th Title
      %th Action

  %tbody
    - @settings.each do |setting|
      %tr
        %td= setting.human_name
        %td= setting.value
        %td
          = link_to 'Edit', edit_admin_setting_path(setting)

setting.rb

class Setting < ActiveRecord::Base

  validates :key, :human_name, presence: true

  after_save do
    @@cached = nil
  end

  def self.value(key)
    @@cached ||= Hash[ pluck(:key, :value) ]
    @@cached[key]
  end
end

settings_controller.rb

class Admin::SettingsController < Admin::ApplicationController
  before_action :set_setting, only: [:edit, :update]

  def index
    @settings = Setting.order('human_name asc')
  end

  def edit
  end

  def update
    if @setting.update(settings_params)
      redirect_to admin_settings_path, notice: 'Setting was successfully updated.'
    else
      render :edit
    end
  end

  private

  def set_setting
    @setting = Setting.find(params[:id])
  end

  def settings_params
    params.require(:setting).permit(:key, :human_name, :value)
  end
end