在Rails中使用object_id列的含义

Question

What are the implications of having a object_id / object_type on a model (for a polymorphic association) in regards to Object itself containing an object_id and that overriding it ( http://ruby-doc.org/core-2.3.1/Object.html#method-i-object_id )?

class Event
  belongs_to :object, polymorphic: true # object_id/object_type
end

Answer 1

When I search for object_id through the whole codebase of one of my rails projects (including all gems), I can see over 200 hits. In Rails only, this is about 50 hits .

I'd expect problems with records comparison, using them as hash keys, putting them to set s, perhaps also duplicating them with dup . In Rails, record.object_id is referenced in caching, has_many_through associations, AREL, pretty printing the record, minitest expectations, also in pry debugger,

But just from quick-looking trough the code it is very hard to guess if it will cause problems or not and I generally tend to be very defensive about such potential problems - you'll never know for sure if your next usage of the object will not break things in a way that is both very hard to debug and perhaps impossible to fix.

As I said above, I'd be very curious if you tried, but myself would rather name it belongs_to :thing, polymorphic: true or better yet something even more specific.

Answer 2

If you attempt to define object_id on a class you'll find that you get the following angry warning from the Ruby interpreter warning: redefining 'object_id' may cause serious problems (try it from IRB). That sounds scary - and the incidents may be tied to specific versions of Ruby (and vary based on the version used). I'd recommend fixing this.

Answer 3

I believe you can belong_to object, while defining the foreign_key to something else, like foreign_key: :object_identifier. That way you dont have to worry about object_id.

Answer 4

我认为最好遵循本文档Active Record Associations ，我认为定义另一个object_id将使您在代码中手动维持关系，并且您将失去Active Record功能。