This plugin allows ActiveRecord to act as view table.

Usage

Let’s consider following table that manages students with two columns “grade” and “deleted”, where “deleted” means logical deletion.

> select * from members;
+----+--------+-------+---------+
| id | name   | grade | deleted |
+----+--------+-------+---------+
|  1 | saki   |     3 |       0 |
|  2 | miyabi |     2 |       0 |
|  3 | maiha  |     2 |       1 |
|  4 | kuma   |     1 |       0 |
+----+--------+-------+---------+

{{{
class Member < ActiveRecord::Base; end
}}}

(1) using “acts_as_view” class method

Define view models by “acts_as_view”.

{{{
class ActiveMember < Member
  acts_as_view :deleted => false
end

class DeletedMember < Member
  acts_as_view :deleted => true
end

class ActiveGrade2Member < Member
  acts_as_view :deleted => false, :grade=>2
end

class InheritedActiveGrade2Member < ActiveMember
  acts_as_view :grade=>2
end
}}}

We can easily read records as same as using DB view table.

{{{
ActiveMember.find(:all)                # => SELECT * FROM members WHERE (( deleted = 'f' ))
DeletedMember.find(:all)               # => SELECT * FROM members WHERE (( deleted = 't' ))
ActiveGrade2Member.find(:all)          # => SELECT * FROM members WHERE (( deleted = 'f' ) AND ( grade = 2 )) 
InheritedActiveGrade2Member.find(:all) # => SELECT * FROM members WHERE (( ( deleted = 'f' ) ) AND ( ( grade = 2 ) )) 
}}}

In addition, we can also write records to the view. Note that “grade” and “deleted” columns automatically set.

{{{
ActiveGrade2Member.create(:name=>"chinako")
# => #"chinako", "grade"=>2, "id"=>5, "deleted"=>false}>
}}}

Furthermore, the view constrain also means a restriction to resources. Note that specified “grade” is ignored because the view table forces all members to be active and grade2.

{{{
ActiveGrade2Member.create(:name=>"momoko", :grade=>3)
# => #"momoko", "grade"=>2, "id"=>6, "deleted"=>false}>
}}}

(2) using “create_view” class method

We can dynamically create view model class represented by anonymous (unnamed) class by using “create_view” class method. This is useful when we need dynamical restrictions.

{{{
my_mails = Mail.create_view(:owner_id=>session[:owner_id])
my_mails.find(:all)
# => "SELECT * FROM mails WHERE ( owner_id = ... )
}}}

Cautions

The above restriction feature is wrong with “AR.create!”, because “acts_as_view” is implemented by “with_scope” which is broken about treating “AR.create!”.

Install

This plugin currently depends on “scoped_access” plugin that offers ScopedAccess::MethodScoping class. So we need those both plugins.

http://wota.jp/svn/rails/plugins/branches/stable/acts_as_view/ http://wota.jp/svn/rails/plugins/branches/stable/scoped_access/