CODEWITHSUNDEEP
ruby-on-rails-4associations
Raja Sharma
Raja Sharma

Reputation: 510

Polymorphic association with condition

We have models as below...

class Post
  has_many: :comments, as: :commentable
end

class Media
  has_many: :comments, as: :commentable
end

class Comment
  belongs_to: :commentable, polymorphic: true
  belongs_to: :post, foreign_key::post_id, foreign_type: 'Post'
end

Exampale

Post1 has Comment3 => {id: 3, text: "Some comment 3", commentable_id: 1, commentable_type: 'Post'}
Media2 has Comment4 => {id: 4, text: "Some comment 4", commentable_id: 2, commentable_type: 'Media'}

When I want to access Comment3.post it gives result as expected.
But When some how want access Comment4.post it brings an object from post table which has id = 2, but expected nil, coz Comment4 does not belongs to any post.

We can get from below method inside Comment model, but want as an association.

def post
  self.commentable if self.commentable_type == 'Post'
end

Could not get what I expected.., Please help here...

Upvotes: 1

Views: 309

Answers (1)

Bachan Smruty
Bachan Smruty

Reputation: 5734

I like your approach

def post
  self.commentable if self.commentable_type == 'Post'
end

But if you really need it in the association way, then you can try with

belongs_to :post, foreign_key: :commentable_id, foreign_type: :commentable_type, polymorphic: true

OR

belongs_to :post, -> (record){ record.commentable_type == 'Post' ? joins(:comments).where(comments: {commentable_type: 'Post'}) : where("false") }, foreign_key: :commentable_id

Hope, it helps.

Upvotes: 2

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