ruby on rails - How do I build a complex nested form to represent dynamic attributes -

i've got data model represented following image:

basically, idea there many different collections. items in single collection have same attributes, list of attributes different per collection. value of each attribute per item stored in item attribute values.

i'm trying build single page user can populate attributes item. i'm assuming nested form way go i'm @ loss how represent in controller , on page, considering names of attributes in 1 table , values in another.

if has encountered or had deal similar situation, appreciated.

thanks

here 1 potential solution.

class collection   has_and_belongs_to_many :items   has_and_belongs_to_many :attributes end  class item   has_and_belongs_to_many :collections   has_many :item_attributes   has_many :attributes, though: :item_attributes end  class attributes   has_and_belongs_to_many :collections   has_many :item_attributes   has_many :items, though: :item_attributes end  class itemattribute   belongs_to :item   belongs_to :attribute end 

so lets @ database layout these models:

activerecord::schema.define(version: 20151027173337)    create_table "attributes_collections", id: false, force: :cascade |t|     t.integer "attribute_id",  null: false     t.integer "collection_id", null: false   end    create_table "collections", force: :cascade |t|     t.string   "title"     t.integer  "user_id"     t.datetime "created_at", null: false     t.datetime "updated_at", null: false   end    add_index "collections", ["user_id"], name: "index_collections_on_user_id"    create_table "collections_items", id: false, force: :cascade |t|     t.integer "collection_id", null: false     t.integer "item_id",       null: false   end    create_table "item_attributes", force: :cascade |t|     t.integer  "item_id"     t.integer  "attribute_id"     t.string   "value"     t.datetime "created_at",   null: false     t.datetime "updated_at",   null: false   end    add_index "item_attributes", ["attribute_id"], name: "index_item_attributes_on_attribute_id"   add_index "item_attributes", ["item_id"], name: "index_item_attributes_on_item_id"    create_table "items", force: :cascade |t|     t.string   "name"     t.datetime "created_at", null: false     t.datetime "updated_at", null: false   end  end 

a better way?

but of course performance suffer due many joins. plus each attribute stored varchar means can't numeric comparisons in database.

if need flexible schema instead using hstore, json or dynamic column type or schemaless database such mongodb.

how create form / controller this?

first should acquainted can done accepts_nested_attributes_for , fields_for , maybe consider using ajax delegate actions out collectioncontroller , itemcontroller on end rather cramming single monstrosity.