has_many through and polymorphic relationships

Question

I don't know if this is possible, but here goes:

FruitBasket
  has_many :apples
  has_many :bananas
  ######## What to put here to access Worm through its pest_holder relationship?
Apple
  has_many :worms, :as => :pest_holder
  belongs_to :fruit_basket
Banana
  has_many :worms, :as => :pest_holder
  belongs_to :fruit_basket
Worm
  belongs_to :pest_holder, :polymorphic => true

What is the relationship I need to be able to call:

red_delicious = Apple.first
red_delicious.worms.whatever

And have it grab all of the Worm's through Apple's and Banana's polymorphic relationship with Worm?

It seems kind of backwards, but I appreciate the help anyway! If there's any clarification needed, just ask.

These questions are **SOOOOOO** much harder to answer with fake model names. — smathy, Jun 08 '11 at 20:25
Ok, so now your sample code is confusing, did you mean to have `FruitBasket` in there somewhere? — smathy, Jun 08 '11 at 20:52
I think he means to be able to grab the fruit_basket through a worm, and grab the worms of a given fruit_basket. — Mario, Jun 08 '11 at 20:54

score 1 · Accepted Answer · answered Jun 08 '11 at 20:59

1

(Guessing the answer to my own comment above)

You can't do what you want to, there's no Rails helper to allow you to join through to Worm from FruitBasket in a single association. You can have apple_worms and banana_worms but I'm sure you guessed that already, and that that's not what you want.

What you'll need to do is to create your own method to get to the correct Worms - something like this:

def worms
  Worm.where :id => apple_ids + banana_ids
end

answered Jun 08 '11 at 20:59

smathy

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Yeah, I was curious if there was a helper to let me do something like that but apparently not. – nbucciarelli Jun 08 '11 at 21:09
It might be nice if `:through => [ :apples, :bananas ]` worked. – smathy Jun 08 '11 at 21:14

has_many through and polymorphic relationships

1 Answers1