ruby-on-rails – Money-Rails Gem：模型中的Humanized_money

我需要模型中捐赠金额的人性化版本(例如643.50),这样我就可以生成并向捐赠者发送PDF收据.

我尝试过humanized_money(self.amount)和self.amount.humanized_money,但是得到了错误：

NoMethodError: undefined method `humanized_money' for #<Donation:0x007fa687ebb678>

如何在模型中获得这种人性化的形式？

class Donation < ActiveRecord::Base
  belongs_to :donatable,polymorphic: true
  belongs_to :added_by_user,foreign_key: "added_by",class_name: "User"

  store_accessor :details,:method

  monetize :amount_cents

  def donations_this_week(branch_id)
    sum =  Donation.sum(:amount_cents).to_money
    return humanized_money(sum)
  end

  def receipt
    Receipts::Receipt.new(
        id: id,product: "GoRails",message: "This receipt is to acknowledge that we have received a donation with the below details from #{self.donatable.name}",company: {
            name: self.donatable.branch.organization.name,address: "#{self.donatable.branch.address_line_1}n#{self.donatable.branch.address_line_2}n#{self.donatable.branch.email}n#{self.donatable.branch.legal_details}",email: self.donatable.branch.email,logo: self.donatable.branch.organization.logo.url(:medium),},line_items: [
            ["Date",created_at.to_s],["Donor Name",self.donatable.name],["Amount",humanized_money(self.amount)],["Payment Method",self.method],]
    )
  end
end

以下是数据库架构：

create_table "donations",force: :cascade do |t|
t.string   "donatable_type"
t.integer  "donatable_id"
t.integer  "amount_cents"
t.datetime "created_at",null: false
t.datetime "updated_at",null: false
t.datetime "date"
t.integer  "added_by"
t.jsonb    "details",default: {},null: false