How to use Ruby on Rails to integrate with a legacy database while leveraging scaffolding.

-
I am trying to be as lazy as possible...

rails_app $ rails independentreps -d mysql
Edit config/database.yml with specific database name, host, username, password. Add additional environment records if required. For example:

development:
  adapter: mysql
  encoding: utf8
  database: indrep_development
  pool: 5
  username: root
  password: pw
  host: localhost

test:
  adapter: mysql
  encoding: utf8
  database: indrep_test
  pool: 5
  username: ...
...
production:
...
  database: indrep_production
...
## Additional Environment Records
legacy_production:
  adapter: mysql
  encoding: utf8
  database: reps_db
  pool: 5
  username: admin
  password: letmein
  host: 192.168.0.10
  port: 13540

From within the application folder, use the generation features of the Ruby on Rails framework
rails_app $ ruby script/generate model Client
rails_app $ ruby script/generate scaffold Client
So scaffolding is generated for the first time.

Next, edit app/models/client.rb with set_table_name, set_primary_key with actual identifiers from legacy database
rails_app $ script/console
>> Client
=> will spit out Ruby-friendly style of describing table schema/model, i.e. Client model. Copy this result to clipboard.
>> exit
rails_app $ rm app/helpers/clients_helper.rb

So we generate scaffolding again, but this time with value-added features of our schema/model attributes.
rails_app $ ruby script/generate scaffold Client <Paste model attributes from clipboard here.> However take out the commas between attributes, and the spaces between the attribute and datatype.
replace files if asked.
rails_app $ mongrel_rails start -d
visit http://localhost:3000/Clients

Why do we generate scaffold twice instead of just once? There is no logical reason for it when the first run creates the controller.rb and view templates (index, new, show, edit), while the second run would do the same, only with the attributes all spelled out. Why not just edit the model client.rb with the legacy table information before running script/generate scaffold? Well for some reason if scaffolding is not generated twice, you will end up with the following error:

ActionController::RoutingError in Clients#index

instead of nice table rows with Show Edit Destroy working links.

I know that generating scaffold twice will add the line map.resoures :clients twice to the config/routes.rb file. But manually duplicating that line in routes.rb does not solve the problem.
One day, when I have the time and am able to understand Ruby better I'll take a look at this article about route generation. I figure it will explain this strange behaviour.
The following shows a part of the Full Trace response generated by this strange problem.

client_url failed to generate from {:action=>"show", :controller=>"clients", :id=>#<Client pkId: 2, Name: "Make It Work Enterprises"...

Extracted source (around line #57):
56: <td><%=h client.IDamandar %></td>
57: <td><%= link_to 'Show', client %></td>
58: <td><%= link_to 'Edit', edit_client_path(client) %></td>

/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/routing/route_set.rb:377:in `raise_named_route_error'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/routing/route_set.rb:341:in `generate'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/url_rewriter.rb:208:in `rewrite_path'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/url_rewriter.rb:187:in `rewrite_url'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/url_rewriter.rb:165:in `rewrite'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:626:in `url_for'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/url_helper.rb:85:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/url_helper.rb:85:in `url_for'
(eval):16:in `client_path'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/polymorphic_routes.rb:112:in `__send__'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/polymorphic_routes.rb:112:in `polymorphic_url'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/polymorphic_routes.rb:119:in `polymorphic_path'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/url_helper.rb:91:in `url_for'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/url_helper.rb:228:in `link_to'
app/views/clients/index.html.erb:107
app/views/clients/index.html.erb:56:in `each'
app/views/clients/index.html.erb:56
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:39:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:39:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/template.rb:73:in `render_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:256:in `render'

Comments

Post a Comment

Popular posts from this blog

Calculating total interest accrued while paying down the simple interest loan periodically.

-
I was unable to find a web service or calculator on any websites that had a simple interest calculator in which the total of the loan was being payed down regularly. I was forced to make one in Excel. There are plenty of amortization calculators out there that generate the schedule for a loan with compound interest, like a mortgage, but none that show the schedule for a simple interest loan, like some HELOCs (in Canada). My Excel spreadsheet allows one to compare an amortization schedule on a compound interest loan to a schedule for a simple interest loan. This is useful if you want to see the affect of making payments on a simple interest loan, equal to the same amount at the same time of the month on the same frequency as you would on a mortgage. The spreadsheet assumes interest for the simple interest loan is calculated daily and that payments against the loan are applied to the interest accrued first, and then toward the principal. It can be tweaked if you wanted to calculate i...
Read more

A list of "All-Weather" tires with the Mountain/Snowflake symbol and where to get them

-
Image
Though the design and compounds have been around a few years now, it was surprisingly difficult to find tires that are truly All-Weather (good for every season) per Transport Canada standards and meet or exceed the Rubber Association of Canada performance requirements. Since my tires need replacing and I'm not looking for soft winter-specific tires, I have compiled a list of tyres that have the mountain/snowflake rating based upon my search. Perhaps you'll find this list useful and that it saves you time. Nokian pioneered this class of tires and was the first to market but there are now a number of brands with a limited selection. http://www.wheels.ca/news/all-weather-tires-are-not-the-same-as-all-season-and-heres-why/ These makes include: Kumho, Toyo, Falken, Michelin, Vredestein, Hankook, Yokohama, and Nankang, Michelin, Multi-Mile, and Muteki.  Additionally, some are exclusively sold at certain retailers. Tires that have the 3PMSF icon and are all-weather cap...
Read more

New annoyances: Windows 7 and Bluetooth enabled devices.

-
Thorough testing on my part has proven that Windows 7 can not receive large files, approximately anything larger than 225 KB, from some Bluetooth devices. In this case, my Nokia 6301 can not send to the "fsquirt.exe" utility on Windows 7. I tested this with 3 different machines running Windows 7 (6.01.7600), two laptops with built-in bluetooth and a desktop using a bluetooth dongle. The error message offers no clue as to why or what happened. All it says is " Bluetooth file transfer not completed " " The transfer was cancelled by the Bluetooth device or Bluetooth enabled computer. " However, the Nokia 6301 has no problem receiving large multi-megabyte files from a PC running Windows 7. The Nokia 6301 is also able to send/receive large files to other devices (phones, PDA's), and computers running Windows XP, Vista, or Mac OS X. On the other hand, Windows 7 was able to receive files over bluetooth from other bluetooth-enabled devices, including: com...
Read more