如何创建读钢轨的型号,没有支持表 [英] How to create read only models in rails with no backing table
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问题描述
我想创建读,可能是一些复杂的结果只会车型 加入或汇总查询,有一点就任何直接表模型类 我已经定义了。
I would like to create read only models that may be the result of some complex join or aggregate query that has little relation to any of the direct table model classes I have defined.
例如虚的ActiveRecord :: View类
For example the imaginary ActiveRecord::View class
class B < ActiveRecord::View
default_scope do
find_by_sql <<-EOF
select x.alpha alpha, y.a_id a_id from
x.join y on x.id = y.id
EOF
end
belongs_to :a
end
class A < ActiveRecord::Base
has_many :b
end
>> a = A.first
>> puts a.id
10
>> puts a.bs.to_sql
select x.alpha alpha, y.a_id a_id from
x.join y on x.id = y.id
where a_id = 10
我相信上述或类似的东西是有的,但我无法找到它。
I am sure the above or something like it is available but I just can't find it.
推荐答案
我已经发布了Ruby的创业板,解决了这个问题。
I've released a Ruby GEM that solves this problem
https://github.com/bradphelan/Active-Illusion
该规范文件验证行为
require 'rubygems'
require 'active_illusion'
require 'squeel'
TIMES = (ENV['N'] || 10000).to_i
require 'rubygems'
require "active_record"
conn = { :adapter => 'sqlite3', :database => ':memory:' }
ActiveRecord::Base.establish_connection(conn)
class User < ActiveRecord::Base
connection.create_table :users, :force => true do |t|
t.string :name, :email
t.timestamps
end
has_many :exhibits
end
class Exhibit < ActiveRecord::Base
connection.create_table :exhibits, :force => true do |t|
t.belongs_to :user
t.string :name
t.text :notes
t.integer :ssn
t.timestamps
end
belongs_to :user
def look; attributes end
def feel; look; user.name end
def self.look(exhibits) exhibits.each { |e| e.look } end
def self.feel(exhibits) exhibits.each { |e| e.feel } end
end
module ActiveRecord
class Faker
LOREM = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse non aliquet diam. Curabitur vel urna metus, quis malesuada elit. Integer consequat tincidunt felis. Etiam non erat dolor. Vivamus imperdiet nibh sit amet diam eleifend id posuere diam malesuada. Mauris at accumsan sem. Donec id lorem neque. Fusce erat lorem, ornare eu congue vitae, malesuada quis neque. Maecenas vel urna a velit pretium fermentum. Donec tortor enim, tempor venenatis egestas a, tempor sed ipsum. Ut arcu justo, faucibus non imperdiet ac, interdum at diam. Pellentesque ipsum enim, venenatis ut iaculis vitae, varius vitae sem. Sed rutrum quam ac elit euismod bibendum. Donec ultricies ultricies magna, at lacinia libero mollis aliquam. Sed ac arcu in tortor elementum tincidunt vel interdum sem. Curabitur eget erat arcu. Praesent eget eros leo. Nam magna enim, sollicitudin vehicula scelerisque in, vulputate ut libero. Praesent varius tincidunt commodo".split
def self.name
LOREM.grep(/^\w*$/).sort_by { rand }.first(2).join ' '
end
def self.email
LOREM.grep(/^\w*$/).sort_by { rand }.first(2).join('@') + ".com"
end
end
end
class Test0 < ActiveRecord::Illusion
column :name
column :exhibition
column :number
#belongs_to :user, :foreign_key => :name
view do
User.joins{exhibits}.select{
[users.name.as(name), exhibits.name.as(xname), exhibits.ssn.as(number) ]
}
end
end
# pre-compute the insert statements and fake data compilation,
# so the benchmarks below show the actual runtime for the execute
# method, minus the setup steps
# Using the same paragraph for all exhibits because it is very slow
# to generate unique paragraphs for all exhibits.
notes = ActiveRecord::Faker::LOREM.join ' '
today = Date.today
describe ActiveRecord::Illusion do
before :each do
User.destroy_all
Exhibit.destroy_all
puts 'Inserting 100 users and exhibits...'
100.times do |i|
user = User.create(
:created_at => today,
:name => ActiveRecord::Faker.name,
:email => ActiveRecord::Faker.email
)
Exhibit.create(
:created_at => today,
:name => ActiveRecord::Faker.name,
:user => user,
:notes => notes,
:ssn => i
)
end
end
it "should have 100 users" do
User.count.should == 100
end
it "should have 100 exhibits" do
Exhibit.count.should == 100
end
describe Test0 do
it "should retrieve 100 rows" do
Test0.where{}.to_sql.should ==
%Q[SELECT \"test0s\".* FROM (SELECT \"users\".\"name\" AS name, \"exhibits\".\"name\" AS xname, \"exhibits\".\"ssn\" AS number FROM \"users\" INNER JOIN \"exhibits\" ON \"exhibits\".\"user_id\" = \"users\".\"id\") test0s ]
Test0.count.should == 100
Test0.where{number < 20}.to_sql.should ==
%Q[SELECT "test0s".* FROM (SELECT "users"."name" AS name, "exhibits"."name" AS xname, "exhibits"."ssn" AS number FROM "users" INNER JOIN "exhibits" ON "exhibits"."user_id" = "users"."id") test0s WHERE "test0s"."number" < 20]
Test0.where{number < 20}.count.should == 20
end
end
end
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