Rails4 - Displaying items in the orders form - ruby-on-rails

Question

I want the user to search through existing items from the items table in the orders form, it works for clients but not for items, it gives an error: Association :item not found
Models
class Order < ActiveRecord::Base
belongs_to :user
belongs_to :client
has_many :order_items
has_many :items, :through => :order_items
end
class Item < ActiveRecord::Base
has_many :order_items
has_many :orders, :through => :order_items
end
class OrderItem < ActiveRecord::Base
belongs_to :item
belongs_to :order
end
Migration
class CreateOrderItems < ActiveRecord::Migration
def change
create_table :order_items do |t|
t.integer :item_id
t.integer :order_id
t.timestamps
end
add_index :order_items, [:item_id, :order_id]
end
end
View
<%= simple_form_for(#order) do |f| %>
<%= f.error_notification %>
<%= f.association :client, collection: Client.all, label_method: :name, value_method: :id, prompt: "Choose a Client", input_html: { id: 'client-select2' } %>
<%= f.association :item, collection: Item.all, label_method: :name, value_method: :id, prompt: "Choose an item", input_html: { id: 'client-select2' } %>
<%= f.input :memo, label: 'Comments' %>
<%= f.submit %>
<% end %>
Controller
def new
#order = Order.new
end
def create
#order = Order.new(order_params)
#order.user_id = current_user.id
#order.status = TRUE
end
def order_params
params.require(:order).permit(:code, :client_id, :user_id, :memo, :status, items_attributes: [:id, :name, :price, :quantity, :status, :_destroy])
end
Answer
In the form use instead:
using rails-select2 gem
<%= f.association :items, collection: Item.all, label_method: :name, value_method: :id, prompt: "Choose an item", input_html: { id: 'item-select2' } %>
or without select2
<%= f.select :item_ids, Item.all.collect {|x| [x.name, x.id]}, {}, multiple: true %>
Thanks to JKen13579

Answer 1

The reason that you're receiving the error for item but not for client is because there is one client associated to an order, but more than one item associated to an order. It's saying :item not found because you should be using :items (note the plural).
To allow multi-select for your order's items, replace your f.association item line with:
<%= f.select :item_ids, Item.all.collect {|x| [x.name, x.id]}, {}, multiple: true %>
And then in your controller, be sure to permit item_ids. In addition, you don't need item_attributes, because you're not using accepted_nested_attributes_for :items.
def order_params
params.require(:order).permit(:code, :client_id, :user_id, :memo, :status, item_ids: [])
end
See this SO answer for more information about has_many :through multi-select.