The latest release of sequel_model includes a new associations functionality written by Jeremy Evans which replaces the old relations code in previous versions. Please note that this version is not completely backward-compatible and you should therefore upgrade with caution.
The new implementation supports three kinds of relations: one_to_many, many_to_one and many_to_many, which correspond to has_many, belongs_to and has_and_belongs_to_many relations in ActiveRecord. In fact, the new implementation includes aliases for ActiveRecord assocation macros and is basically compatible with ActiveRecord conventions. It also supports DRY implicit class name references. Here’s a simple example:
class Author < Sequel::Model has_many :books # equivalent to one_to_many end class Book < Sequel::Model belongs_to :author # equivalent to many_to_one has_and_belongs_to_many :categories # equivalent to many_to_many end class Category < Sequel::Model has_and_belongs_to_many :books end
These macros will create the following methods:
Author#books, Author#add_book, Author#remove_book
Book#author, Book#categories, Book#add_category,
Category#books, Category#add_book, Category#remove_book
Unlike ActiveRecord, one_to_many and many_to_many association methods return a dataset:
a = Author a.books.sql #=> 'SELECT * FROM books WHERE (author_id = 1234)'
You can also tell
Sequel to cache the association result set and return it as an array:
class Author < Sequel::Model has_many :books, :cache => true end Author.books.class #=> Array
You can of course bypass the defaults and specify class names and key names:
class Node < Sequel::Model belongs_to :parent, :class => Node belongs_to :session, :key => :producer_id end
Another useful option is :order, which sets the order for the association dataset:
class Author < Sequel::Model has_many :books, :order => :title end Author.books.sql #=> 'SELECT * FROM books WHERE (author_id =
1234) ORDER BY title’
More information about associations can be found in the
Added configuration file for running specs (#186).
Changed Database#drop_index to accept fixed arity (#173).
Changed column definition sql to put UNSIGNED constraint before
unique in order to satisfy MySQL (#171).
Enhanced MySQL adapter to support load data local infile_, added
compress option for mysql connection by default (#172).
Fixed bug when inserting hashes in array tuples mode.
Changed SQLite adapter to catch RuntimeError raised when executing a
statement and raise Error::InvalidStatement with the offending SQL and error message (#188).
Fixed Dataset#reverse to not raise for unordered dataset (#189).
Added Dataset#unordered method and changed order to remove order if
nil is specified (#190).
Fixed reversing order of ASC expression (#164).
Added support for :null => true option when defining table columns
Fixed Symbol#method_missing to accept variable arity (#185).