指定在belongsToMany-through關聯中的外鍵

Question

我想在CakePHP 3.0中使用belongsToMany-through關聯時設置使用的外鍵。

考慮下面兩個表：

實體：ID，標題
鏈接：ID，from_id，to_id，additional_information

我使用額外的，因爲belongsToMany，通過協會我需要在直通表中存儲信息。

下面是這兩個表類：

class LinksTable extends AppTable 
{ 
    public function initialize(array $config) { 
     parent::initialize($config); 

     $this->belongsTo('FromEntities', [ 
      'className' => 'Entity', 
      'foreignKey' => 'from_id' 
     ]); 
     $this->belongsTo('ToEntities', [ 
      'className' => 'Entity', 
      'foreignKey' => 'to_id' 
     ]); 
    } 
} 

class EntitiesTable extends AppTable 
{ 
    public function initialize(array $config) { 
     parent::initialize($config); 

     $this->belongsToMany('Entities', [ 
      'through' => 'Links' 
     ]); 
    } 
} 

但當然CakePHP中試圖加入表使用默認的外鍵entity_id，這是不正確的。

如何定義用於連接EntitiesTable類中的表的外鍵？

編輯：爲了完整起見，在這裏試圖用$this->Entities->findById(1)->contain('Entities');協會獲取實體時是錯誤信息和生成的查詢。

Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Links.entity_id' in 'field list'

SELECT Links.entity_id AS `Links__entity_id`, Links.id AS `Links__id`, Links.from_id AS `Links__from_id`, Links.to_id AS `Links__to_id`, Links.type AS `Links__type`, Links.role AS `Links__role`, Entities.id AS `Entities__id`, Entities.type AS `Entities__type`, Entities.title AS `Entities__title`, Entities.user_id AS `Entities__user_id`, Entities.created AS `Entities__created` FROM entities Entities INNER JOIN links Links ON Entities.id = (Links.entity_id) WHERE Links.entity_id in (:c0) 

有在我剝離出來的代碼示例上面，如果你想知道生成的查詢一些附加字段。

Answer 1

經過一些測試用例的挖掘，我找到了答案this test。

belongsToMany有一個未公開的選項targetForeignKey，所以EntitiesTable類應該是這樣的方法：

class EntitiesTable extends AppTable 
{ 
    public function initialize(array $config) { 
     parent::initialize($config); 

     $this->belongsToMany('LinkedEntities', [ 
      'className' => 'Entities', 
      'through' => 'Links', 
      'foreignKey' => 'from_id', 
      'targetForeignKey' => 'to_id' 
     ]); 
    } 
} 

現在我能夠使用訪問鏈接的實體$this->Entities->findById(1)->contain('LinkedEntities');