admin_gen.rb

require 'rubygems'
require 'sinatra'
require 'activerecord'

#db settings
ActiveRecord::Base.establish_connection(
  :adapter => '',
  :encoding => '',
  :database => '',
  :username => '',
  :password => '',
  :host => ''
)

#add models here:
models = %w(User Post Comment)

models.each do |k|
  eval "class #{k} < ActiveRecord::Base ; end"
end


class Resource
  attr_accessor :name, :klass, :instance

  def initialize(name)
    @name = name.camelcase
    @klass = eval(@name)
    @instance = @klass.find(:all, :limit => 1).first || @klass.new
  end
end

get '/' do
  @models = models
  erb :menu
end

get '/:model/index' do
  @resource   = Resource.new(params[:model])
  @name       = @resource.name.underscore.singularize
  erb :index
end

get '/:model/form' do
  @resource   = Resource.new(params[:model])
  @name       = @resource.name.underscore.singularize
  erb :form
end

def styles
  <<-CSS
  <style>
    textarea {width:100%; height:100%; font-size: 14px;}
    body { font-size: 18px }
  </style>
  CSS
end

__END__

@@ menu
<%= styles %>
<ul>
  <% @models.each do |model| %>
    <li>
      <%= model %>
      <a href="/<%= model %>/index">index</a>
      <a href="/<%= model %>/form">form</a>
    </li>
  <% end %>
</ul>

@@ index
<%= styles %>
<a href="/">Back</a>
<textarea style="width:100%;height:100%">
<table>
  <tr>
    <% @resource.instance.attribute_names.each do |attribute_name| %><td><%=
      attribute_name.humanize %></td>
    <% end %>
    <td></td>
  </tr>
  <%% @<%= @name.pluralize %>.each do |<%= @name %>| %>
    <tr><% @resource.instance.attribute_names.each do |attribute_name| %>
      <td><%%= <%= @name %>.<%= attribute_name %> %></td><% end %>
      <td>(<%%= link_to 'edit', edit_admin_<%= @name %>_path(<%= @name %>) %>)</td>
    </tr>
  <%% end %>
</table>
</textarea>

@@ form
<%= styles %>
<a href="/">Back</a>
<textarea style="width:100%;height:100%">
<%% form_for [:admin, @<%= @resource.name.underscore %>] do |f| %>
  <% @resource.instance.attribute_names.each do |attribute_name| %>
  <div>
    <%%= f.label :<%= attribute_name %>, '<%= attribute_name.humanize %>', :class => 'attribute_name' %>
    <%%= f.text_field :<%= attribute_name  %> %>
  </div>
  <% end %>
<%% end %>
</textarea>