The Database

Two words about the database:

Organizations

Departments/Organizations/Bunkers, you name it. In my University are just organizational units each with its own money to buy toners.

Vendors

Just a list of vendors (HP, Kyocera...)

Printer_models and toner_models

Common to all organizations are printer_models:

+-----------+--------------+------+-----+---------+----------------+
| Field     | Type         | Null | Key | Default | Extra          |
+-----------+--------------+------+-----+---------+----------------+
| id        | int(11)      | NO   | PRI | NULL    | auto_increment |
| vendor_id | int(11)      | NO   | MUL | NULL    |                |
| name      | varchar(255) | YES  |     | NULL    |                |
| laser     | tinyint(1)   | YES  |     | NULL    |                |

and toner_models:

+------------+--------------+------+-----+---------+----------------+
| Field      | Type         | Null | Key | Default | Extra          |
+------------+--------------+------+-----+---------+----------------+
| id         | int(11)      | NO   | PRI | NULL    | auto_increment |
| vendor_id  | int(11)      | NO   | MUL | NULL    |                |
| name       | varchar(255) | YES  |     | NULL    |                |
| compatible | tinyint(1)   | YES  |     | NULL    |                |
+------------+--------------+------+-----+---------+----------------+

association table between printer_models and toner_models

is done with the table printer_models_toner_models

+------------------+---------+------+-----+---------+-------+
| Field            | Type    | Null | Key | Default | Extra |
+------------------+---------+------+-----+---------+-------+
| printer_model_id | int(11) | NO   | MUL | NULL    |       |
| toner_model_id   | int(11) | NO   | MUL | NULL    |       |
+------------------+---------+------+-----+---------+-------+

in order to have

class TonerModel < ActiveRecord::Base
  belongs_to :vendor
  has_and_belongs_to_many :printer_models

and

class PrinterModel < ActiveRecord::Base
  belongs_to :vendor
  has_and_belongs_to_many :toner_models

note: vendor in PrinterModel or TonerModel do not have to be the same. Xerox for example makes toners for HP (compatible).

Printers and toners

Every organization has a list of printers and toners.

Printers

+------------------+------------------+------+-----+---------+----------------+
| Field            | Type             | Null | Key | Default | Extra          |
+------------------+------------------+------+-----+---------+----------------+
| id               | int(11) unsigned | NO   | PRI | NULL    | auto_increment |
| organization_id  | int(11) unsigned | YES  | MUL | NULL    |                |
| printer_model_id | int(11) unsigned | YES  | MUL | NULL    |                |
| name             | varchar(255)     | YES  |     | NULL    |                |
| description      | text             | YES  |     | NULL    |                |
| rent             | tinyint(1)       | YES  |     | NULL    |                |
+------------------+------------------+------+-----+---------+----------------+

Toners

+-----------------+------------------+------+-----+---------+----------------+
| Field           | Type             | Null | Key | Default | Extra          |
+-----------------+------------------+------+-----+---------+----------------+
| id              | int(11) unsigned | NO   | PRI | NULL    | auto_increment |
| organization_id | int(11) unsigned | YES  | MUL | NULL    |                |
| toner_model_id  | int(11) unsigned | YES  | MUL | NULL    |                |
| number          | int(11) unsigned | YES  |     | 0       |                |
| gift            | tinyint(1)       | YES  |     | NULL    |                |
+-----------------+------------------+------+-----+---------+----------------+

The toners can be marked as obsolete for the organization (usually the printer is broken or dismissed) by setting true to gift column.

This kind of toners are shown to organizations with compatible printers can be asked.