オブジェクトから値を抽出するにはどうすればよいですか？

Question

--- 
- !ruby/object:Comment 
    attributes: 
    post_id: '5' 
    changed_attributes: {} 
    previously_changed: {} 
    attributes_cache: {} 
    marked_for_destruction: false 
    destroyed: false 
    readonly: false 
    new_record: false 
- !ruby/object:Comment 
    attributes: 
    post_id: '6' 
    changed_attributes: {} 
    previously_changed: {} 
    attributes_cache: {} 
    marked_for_destruction: false 
    destroyed: false 
    readonly: false 
    new_record: false 
- !ruby/object:Comment 
    attributes: 
    post_id: '3' 
    changed_attributes: {} 
    previously_changed: {} 
    attributes_cache: {} 
    marked_for_destruction: false 
    destroyed: false 
    readonly: false 
    new_record: false 
- !ruby/object:Comment 
    attributes: 
    post_id: '7' 
    changed_attributes: {} 
    previously_changed: {} 
    attributes_cache: {} 
    marked_for_destruction: false 
    destroyed: false 
    readonly: false 
    new_record: false 
- !ruby/object:Comment 
    attributes: 
    post_id: '1' 
    changed_attributes: {} 
    previously_changed: {} 
    attributes_cache: {} 
    marked_for_destruction: false 
    destroyed: false 
    readonly: false 
    new_record: false 

（http://pastebin.com/J1angM6d）

どのように私は配列としてpost_idの値を得ることができますか？ @arr = [ 5,6,3,7,1 ] これでこの投稿を取得したいと考えていますpost_id これが正しいですか？ @p = Post.where(:id=>@arr)

Answer 1

@p = Post.find(my_collection.map(&:post_id))