gistfile1.txt

#!/usr/bin/env ruby
# datamapper woes

# Case one: adding an object to an association using << blows up
# Case two: setting an association with a new array doesn't clear
#           out the old one, it just combines them

# output:
# line 49: post.tags << t1 # => #<DataMapper::Associations::ImmutableAssociationError: You can not modify this association>
# line 74: book.authors == [ a1 ] # => true
# line 79: book.authors == [ a2 ] # => false
# line 80: book.authors # => [#<Author id=1>, #<Author id=2>]

require 'rubygems'
require 'dm-core' # on both 0.9.6 and 0.9.7[ba7a38]

class Tagging
  include DataMapper::Resource
  property :id, Serial
  belongs_to :post
  belongs_to :tag
end

class Post
  include DataMapper::Resource
  property :id, Serial
  has n, :taggings
  has n, :tags, :through => :taggings
end

class Tag
  include DataMapper::Resource
  property :id, Serial
  has n, :taggings
  has n, :posts, :through => :taggings
end

# DataMapper::Logger.new(STDERR, :debug)
DataMapper.setup(:default, 'sqlite3::memory:')
DataMapper.auto_migrate!

post = Post.create
t1 = Tag.create
t2 = Tag.create

begin
  post.tags << t1
rescue => e
  puts "line #{__LINE__}: post.tags << t1 # => #{e.inspect}"
end


class Book
  include DataMapper::Resource
  property :id, Serial
  has n, :authors, :through => Resource
end

class Author
  include DataMapper::Resource
  property :id, Serial
  has n, :books, :through => Resource
end

DataMapper.auto_migrate!

book = Book.create
a1 = Author.create
a2 = Author.create

book.authors << a1
book.save
book.reload
puts "line #{__LINE__}: book.authors == [ a1 ] # => #{book.authors == [ a1 ]}"

book.authors = [ a2 ]
book.save
book.reload
puts "line #{__LINE__}: book.authors == [ a2 ] # => #{book.authors == [ a2 ]}"
puts "line #{__LINE__}: book.authors # => #{book.authors.inspect}"