It happens from time to time that we need to associate Models which do not share a common key. An example of this is when I needed to associate pages with templates in a complex join where the PageSettings Model has a primary key of pageid and the PageTemplate Model has a primary key of template_id. We cannot use the primaryKey index of the association array to indicate the relationship, so we need to bypass that index altogether and instead use ‘conditions’ to specify the relationship as follows:
var $hasOne = array('PageTemplate' => array('foreignKey' => false, 'conditions' => array('PageSettings.page_template = PageTemplate.template_id')));
Note also that the ‘conditions’ clause is set using explicit conditions, inasmuch as we are stating that the PageSettings.page_template in the current query should be the same as the PageTemplate.template_id value. I’ve personally been confused in the past, thinking that the ‘PageSettings.page_template’ => ‘PageTemplate.template_id’ formula would naturally be the preferred way of forming the condition in CakePHP. Certainly, that would make sense based on convention, but for reasons I’m not familiar with, this is not how they do it.