Rails嵌套表单无法保存

Question

我有一个表单，其中Application模型接受个人属性和Contact属性。联系人属性依次接受移动属性。我在第11行NoMethodError in ApplicationsController#create获得了undefined method 'mobile' for #<Mobile:0x007fe7d5755318>和if @application.save!。

我的applications_controller.rb如下：

class ApplicationsController < ApplicationController
  def new
    @application = Application.new
    @application.build_personal
    contact = @application.build_contact
    2.times { contact.mobiles.build }
  end

  def create
    @application = Application.new(application_params)
    if @application.save!
      flash[:success] = "Your application has been submitted successful"
      redirect_to root_path #need to be changed
    else
      flash[:alert] = "Some error occured please try again"
      render :new
    end
  end

  def index
  end

  private

  def application_params
    params.require(:application).permit( personal_attributes: [:first_name, :last_name, :fathers_name, :mothers_name, :middle_name, :blood_group, :gender, :religion, :caste, :date_of_birth],
                                         contact_attributes: [:phone, mobiles_attributes: [:id, :mobile_no]])
  end
end

我的contact.rb如下：

class Contact < ActiveRecord::Base
  belongs_to :application
  has_many :mobiles, dependent: :destroy
  accepts_nested_attributes_for :mobiles, reject_if: lambda {|attributes| attributes['mobile_no'].blank?}
end

我的application.rb如下：

class Application < ActiveRecord::Base
  has_one :personal, dependent: :destroy
  has_one :contact, dependent: :destroy
  accepts_nested_attributes_for :personal
  accepts_nested_attributes_for :contact

  before_save :generate_appid

  private

  def generate_appid
    self.app_id = (Application.last.id+1)+1000
  end
end

我的mobile.rb如下：

class Mobile < ActiveRecord::Base
  belongs_to :contact
  validates :mobile, presence: true, numericality: { only_integer: true }
end