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@mayo
Created August 6, 2009 04:24
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b = Book.get(1)
b.latest_page #=> yields Page with id 3, as if I did Page.first(:order => [ :book_id.desc ])
#if I replace the line in latest_page with
self.pages.first(:book_id => self.id, :order => [ :created_at.desc ])
b.latest_page #=> yields Page with id 2, as expected
#if I replace the line in latest_page with
self.pages.first
#this one is with big assumption that without ORDER BY in SELECT statement the DB returns
#the last created/modified entry (which is true for Postgres -- what I use in this case)
#and that page with id 3 was created after page with id 2 was created after page with id 1
b.latest_page #=> returns Page with id 2, as expected with the above assumption
require 'rubygems'
require 'dm-core'
require 'spec'
class Book
include DataMapper::Resource
property :id, Serial
property :title, String
has n, :pages
def latest_page
self.pages.first(:order => [ :created_at.desc ])
end
end
class Page
include DataMapper::Resource
property :id, Serial
property :book_id, Integer
property :created_at, Date
belongs_to :book
end
describe "association scoping problem?" do
before(:each) do
DataMapper.setup(:default, "sqlite3::memory:")
Book.auto_migrate!
Page.auto_migrate!
@book_1 = Book.create(:title => "War and Peace")
@page_1_1 = Page.create(:book_id => @book_1.id, :created_at => "2009-01-01")
@page_1_2 = Page.create(:book_id => @book_1.id, :created_at => "2009-01-02")
@book_2 = Book.create(:title => "The History of the Decline and Fall of the Roman Empire")
@page_2_1 = Page.create(:book_id => @book_2.id, :created_at => "2009-02-01")
end
it "should return same as expected for book 1" do
lookup = @book_1.pages.first(:order => [ :created_at.asc ])
expected = @page_1_1
puts lookup.inspect
puts expected.inspect
lookup.should == expected
end
it "should return same as expected for book 1" do
lookup = @book_1.latest_page
expected = @page_1_2
puts lookup.inspect
puts expected.inspect
lookup.should == expected
end
it "should return same as explicitly scoped lookup for book 1" do
lookup = @book_1.latest_page
expected = @page_1_2
puts lookup.inspect
puts expected.inspect
lookup.should == expected
end
it "should return same as expected for book 2" do
lookup = @book_2.latest_page
expected = @page_2_1
puts lookup.inspect
puts expected.inspect
lookup.should == expected
end
end
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