我在自引用关联方面遇到问题，模型应该为left_chunks和right_chunks方法提供一组模型，但每次都得到一个空数组
来源
class Chunk < ActiveRecord::Base
has_many :left_bindings, :foreign_key => "left_chunk_id",
:class_name => "ChunkChunk",
:dependent => :destroy
has_many :right_chunks, :through => :left_bindings
has_many :right_bindings, :foreign_key => "right_chunk_id",
:class_name => "ChunkChunk",
:dependent => :destroy
has_many :left_chunks, :through => :right_bindings
end
class ChunkChunk < ActiveRecord::Base
belongs_to :left_chunk, :class_name => "Chunk", :foreign_key => "left_chunk_id"
belongs_to :right_chunk, :class_name => "Chunk", :foreign_key => "right_chunk_id"
end
./script/console
的输出>> #first case
?>
?> left = Chunk.new({:content => "chunk_one"}); left.save
=> true
>> right = Chunk.new({:content => "chunk_two"}); right.save
=> true
>> left.right_chunks << right
=> []
>> left.right_chunks
=> []
>> left.left_chunks
=> []
>>
?> #second case
?>
?> left = Chunk.new({:content => "chunk_three"}); left.save
=> true
>> right = Chunk.new({:content => "chunk_four"}); right.save
=> true
>> right.left_chunks << left
=> []
>> right.left_chunks
=> []
>> right.right_chunks
=> []
为什么这些块没有捆绑在一起？
代码执行后的数据库
mysql> select * from chunks;
+----+-------------+---------------------+---------------------+
| id | content | created_at | updated_at |
+----+-------------+---------------------+---------------------+
| 1 | chunk_one | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
| 2 | chunk_two | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
| 3 | chunk_three | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
| 4 | chunk_four | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
+----+-------------+---------------------+---------------------+
mysql> select * from chunk_chunks;
+----+---------------+----------------+---------------------+---------------------+
| id | left_chunk_id | right_chunk_id | created_at | updated_at |
+----+---------------+----------------+---------------------+---------------------+
| 1 | NULL | 2 | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
| 2 | 3 | NULL | 2010-02-14 12:11:22 | 2010-02-14 12:11:22 |
+----+---------------+----------------+---------------------+---------------------+
有什么想法吗？
答案 0 :(得分：3)
您没有说明您使用的是什么版本的MySQL，Ruby或Rails。我刚用一个小测试应用程序尝试了这个，它运行正常。我在OS X 10.6上使用PostgreSQL 8.4.1。我刚刚使用“rails testapp”在Rails 2.3.5 / Ruby 1.8.7（2009-06-12 patchlevel 174）上创建了一个空的应用程序，然后在chunk.rb中添加了两个模型：
class Chunk < ActiveRecord::Base
has_many :left_bindings, :foreign_key => "left_chunk_id",
:class_name => "ChunkChunk",
:dependent => :destroy
has_many :right_chunks, :through => :left_bindings
has_many :right_bindings, :foreign_key => "right_chunk_id",
:class_name => "ChunkChunk",
:dependent => :destroy
has_many :left_chunks, :through => :right_bindings
end
...和chunk_chunks.rb：
class ChunkChunk < ActiveRecord::Base
belongs_to :left_chunk, :class_name => "Chunk", :foreign_key => "left_chunk_id"
belongs_to :right_chunk, :class_name => "Chunk", :foreign_key => "right_chunk_id"
end
...加上两次迁移来添加表格，没有时间戳以简洁：
class AddChunks < ActiveRecord::Migration
def self.up
create_table 'chunks' do | t |
t.string :content
end
end
def self.down
drop_table 'chunk'
end
end
...和
class AddChunkChunks < ActiveRecord::Migration
def self.up
create_table 'chunk_chunks' do | t |
t.belongs_to :left_chunk
t.belongs_to :right_chunk
end
end
def self.down
end
end
然后我运行了“rake db：create”，“rake db：migrate”，你的控制台命令对我有用，如下所示：
PondPro:testapp adh1003$ script/console
Loading development environment (Rails 2.3.5)
>> left = Chunk.new({:content => "chunk_one"}); left.save
=> true
>> right = Chunk.new({:content => "chunk_two"}); right.save
=> true
>> left.right_chunks << right
=> [#<Chunk id: 2, content: "chunk_two">]
>> left.right_chunks
=> [#<Chunk id: 2, content: "chunk_two">]
>> left.left_chunks
=> []
>> left = Chunk.new({:content => "chunk_three"}); left.save
=> true
>> right = Chunk.new({:content => "chunk_four"}); right.save
=> true
>> right.left_chunks << left
=> [#<Chunk id: 3, content: "chunk_three">]
>> right.left_chunks
=> [#<Chunk id: 3, content: "chunk_three">]
>> right.right_chunks
=> []
以上之后的数据库内容是：
chunk-devel=# SELECT * FROM chunks;
id | content
----+-------------
1 | chunk_one
2 | chunk_two
3 | chunk_three
4 | chunk_four
(4 rows)
chunk-devel=# SELECT * FROM chunk_chunks;
id | left_chunk_id | right_chunk_id
----+---------------+----------------
1 | 1 | 2
2 | 3 | 4
(2 rows)
鉴于此：
......而且这个：
...我原来的代码看不出任何问题。也许迁移不是你所期望的，也许你的代码的其他部分你没有发布干扰（例如过滤器，其他宝石）或者MySQL的ActiveRecord数据库适配器在这种情况下没有做正确的事情和/或MySQL运行不正常。安装PostgreSQL并使用它代替MySQL进行进一步测试有点啰嗦，但我认为这是值得的。
以防万一有用，我已经在这里上传了测试应用程序数据：
如果您发现问题并设法纠正错误，请在此处发布后续信息。如果将来遇到类似的麻烦并在搜索解决方案时读取此线程，这将非常有用。
答案 1 :(得分：0)
这是一个.reload问题吗？在控制台中执行此操作后：
right.left_chunks << left
做
right.reload
然后尝试
right.left_chunks。