How to post AngularJS json array to Rails backend api?

I have a list and each list may contain 0 or more items. I'm new to Angularjs and I'm using angularJS $resource to to POST to my rails backend API for creating this list with items. If I create a test array like below and use ListItem.save $scope.test then this POST completes successfully to my Rails backend api.

$scope.test = 'item_id': '55' 'qty': '6' 'uom': 'each'

Processing by Api::V1::ListItemsController#create as JSON

Parameters: {"item_id"=>"55", "qty"=>"6", "uom"=>"each", "list_id"=>"14", "list_item"=>{"item_id"=>"55", "qty"=>"6", "uom"=>"each"}} List Load (0.1ms) SELECT "lists".* FROM "lists" WHERE "lists"."id" = ? LIMIT 1 [["id", 14]] (0.1ms) begin transaction SQL (0.3ms) INSERT INTO "list_items" ("item_id", "qty", "uom", "list_id", "created_at", "updated_at") VALUES (?, ?, ?, ?, ?, ?) [["item_id", 55], ["qty", 6], ["uom", "each"], ["list_id", 14], ["created_at", "2015-06-06 06:14:12.844167"], ["updated_at", "2015-06-06 06:14:12.844167"]] (2.0ms) commit transaction Completed 200 OK in 7ms (Views: 0.5ms | ActiveRecord: 2.6ms) woohoo!!!

However things quickly fall apart when I create a json array in my controller and try to save this array. Then this does not complete successfully (error below)

[ { "item_id": 32, "qty": "1", "uom": "Dozen" } ]

Processing by Api::V1::ListItemsController#create as JSON

Parameters: {"_json"=>[{"item_id"=>34, "qty"=>"1", "uom"=>"Each"}], "list_id"=>"14", "list_item"=>{}} List Load (0.1ms) SELECT "lists".* FROM "lists" WHERE "lists"."id" = ? LIMIT 1 [["id", 14]] Completed 400 Bad Request in 2ms ActionController::ParameterMissing (param is missing or the value is empty: list_item): app/controllers/api/v1/list_items_controller.rb:50:in listItem_params' app/controllers/api/v1/list_items_controller.rb:21:increate'

I even tried to add the list_item object to the json array using ListItem.save {list_item: $scope.final} and then a different error is received below.

Processing by Api::V1::ListItemsController#create as JSON

Parameters: {"list_item"=>[{"item_id"=>30, "qty"=>"1", "uom"=>"Each"}], "list_id"=>"14"} List Load (0.1ms) SELECT "lists".* FROM "lists" WHERE "lists"."id" = ? LIMIT 1 [["id", 14]] Completed 500 Internal Server Error in 2ms NoMethodError (undefined method permit' for [{"item_id"=>30, "qty"=>"1", "uom"=>"Each"}]:Array): app/controllers/api/v1/list_items_controller.rb:50:inlistItem_params' app/controllers/api/v1/list_items_controller.rb:21:in `create'

list_items_controller

    module Api
  module V1
class ListItemsController < ApplicationController
  protect_from_forgery
  skip_before_action :verify_authenticity_token, :if => Proc.new { |c| c.request.format == 'application/json' }
  before_action :set_list
  respond_to :json

  def index
    respond_with ListItem.all
  end

  def new
  end

  def create
    @li = @list.list_items.new(listItem_params)
      if @li.save
        render :status => 200,
           :json => { :success => true,
                      :info => "ItemAdded",
                      :data => { :item => @li }}
      else
        render :status => :unprocessable_entity,
           :json => { :success => false,
                      :info => resource.errors,
                      :data => {} }                              
      end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_list
      @list = List.find(params[:list_id])
    end

    def listItem_params
      params.require(:list_item).permit(:list_id, :item_id, :qty, :uom)
           end
      protected

        def json_request?
          request.format.json?
        end
    end
  end
end

lists.coffee (relevant sections)

    app = angular.module('myApp', [ 'ngResource' ])

ListItem = app.factory('ListItem', ($resource) ->

  $resource '/api/v1/lists/14/list_items/:id', { id: '@id' }, update: method: 'PUT'
)
app.controller 'myCtrl', ($scope, ListItem) ->
  $scope.selection = []
  $scope.final = []
  $scope.test =
  'item_id': '55'
  'qty': '6'
  'uom': 'each'

  $scope.saveListItems = ()->
    i = 0
    while i < $scope.selection.length
      obj = $scope.selection[i]
      $scope.final.push 
        'item_id': obj.id
        'qty': obj.qty
        'uom': obj.uom
      li= ""
      li = ListItem.save $scope.final
      i++

selection array will contain the following for example when I add an item to the selection.

[
  {
    "id": 32,
    "name": "Eggs",
    "created_at": "2015-04-29T00:14:19.627Z",
    "updated_at": "2015-04-29T00:14:19.627Z",
    "user_id": null,
    "qty": "1",
    "uom": "Dozen"
  }
 ]

And when I click the confirm button then the saveListItems function is executed

<button class="btn btn-lg btn-primary" ng-click="saveListItems()">Confirm</button>

the final array contains the following after the saveListItems function is run:

[
  {
    "item_id": 32,
    "qty": "1",
    "uom": "Dozen"
  }
]

I would like to have angularjs build the array correctly so that it will POST a new list item successfully to my rails backend api. Any suggestions on how to fix this?