admin_gen.rb

require 'sinatra'
require 'activerecord'

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

#add models here:
class User < ActiveRecord::Base
end


class Resource
  attr_accessor :name, :klass, :instance

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

  def decamelize
    self.name.to_s.split(/(?=[A-Z])/).join('_').downcase.pluralize
  end
end

get '/' do
  @resource = Resource.new('User')
  erb :index
end

get '/form' do
  @resource = Resource.new('User')
  erb :form
end

__END__


@@ index
<textarea>
<table border="1">
  <tr>
    <% @resource.instance.attribute_names.each do |attribute_name| %>
      <td><%= attribute_name %></td>
    <% end %>
    <td></td>
    <td></td>
  </tr>
  <%% @<%= @resource.decamelize %>.each do |<%= @resource.decamelize.singularize %>| %>
  <tr>
    <% @resource.instance.attribute_names.each do |attribute_name| %>
      <td><%%= <%= @resource.decamelize.singularize %>.<%= attribute_name %> %></td>
    <% end %>
        <td>(<a href="/admin/edit/<%= @resource.decamelize.singularize %>/<%%= <%= @resource.decamelize.singularize %>.id %>">edit</a>)</td>
        <td>(<a href="/admin/view/<%= @resource.decamelize.singularize %>/<%%= <%= @resource.decamelize.singularize %>.id %>">view</a>)</td>
  </tr>
  <%% end %>
</table>
</textarea>

@@ form
<textarea>
  <% @resource.instance.attribute_names.each do |attribute_name| %>
    <p><%= attribute_name %><input type='text' name='<%= @resource.decamelize.singularize %>[<%= attribute_name %>]' value='<%%= @<%= @resource.decamelize.singularize %>.<%= attribute_name %> %>' /></p>
  <% end %>
</textarea>

Check this out. I made a version that's a bit easier to customize when adding models.

The main route, /, is now a menu of the configured models, with links to their respective index and form.

gist 420990