Defining tables and classes (using MySQL) in Ruby on Rails
By: David Heinemeier Hansson in Ruby Tutorials on 2009-03-03
Data definitions are specified only in the database. Active Record queries the database for the column names (that then serves to determine which attributes are valid) on regular object instantiation through the new constructor and relies on the column names in the rows with the finders.
# CREATE TABLE companies ( # id int(11) unsigned NOT NULL auto_increment, # client_of int(11), # name varchar(255), # type varchar(100), # PRIMARY KEY (id) # )
Active Record automatically links the "Company" object to the "companies" table
class Company < ActiveRecord::Base
has_many :people, :class_name => "Person"
end
class Firm < Company
has_many :clients
def people_with_all_clients
clients.inject([]) { |people, client| people + client.people }
end
end
The foreign_key is only necessary because we didn't use "firm_id" in the data definition
class Client < Company
belongs_to :firm, :foreign_key => "client_of"
end
# CREATE TABLE people (
# id int(11) unsigned NOT NULL auto_increment,
# name text,
# company_id text,
# PRIMARY KEY (id)
# )
Active Record will also automatically link the "Person" object to the "people" table
class Person < ActiveRecord::Base
belongs_to :company
end
Add Comment
This policy contains information about your privacy. By posting, you are declaring that you understand this policy:
- Your name, rating, website address, town, country, state and comment will be publicly displayed if entered.
- Aside from the data entered into these form fields, other stored data about your comment will include:
- Your IP address (not displayed)
- The time/date of your submission (displayed)
- Your email address will not be shared. It is collected for only two reasons:
- Administrative purposes, should a need to contact you arise.
- To inform you of new comments, should you subscribe to receive notifications.
- A cookie may be set on your computer. This is used to remember your inputs. It will expire by itself.
This policy is subject to change at any time and without notice.
These terms and conditions contain rules about posting comments. By submitting a comment, you are declaring that you agree with these rules:
- Although the administrator will attempt to moderate comments, it is impossible for every comment to have been moderated at any given time.
- You acknowledge that all comments express the views and opinions of the original author and not those of the administrator.
- You agree not to post any material which is knowingly false, obscene, hateful, threatening, harassing or invasive of a person's privacy.
- The administrator has the right to edit, move or remove any comment for any reason and without notice.
Failure to comply with these rules may result in being banned from submitting further comments.
These terms and conditions are subject to change at any time and without notice.
|
Most Viewed Articles (in Ruby ) |
Latest Articles (in Ruby) |
Comments