Rails：表单帮助——提供带参数的方法

Question

我对 Rails 比较陌生，并尝试编写一个小型贷款应用程序，用户可以在其中向某人贷款，并且该应用程序可以跟踪余额等。我正在向贷款模型添加一个处理付款的功能，并拥有走到这一步（提请注意make_payment(value) 部分：

loan.rb

class Loan < ActiveRecord::Base
  belongs_to :lender, :class_name => 'User'
  belongs_to :borrower, :class_name => 'User'
  has_many :payments

  default_scope -> { order(created_at: :desc) }

  validates :amount, presence: true
  validates :lender, presence: true
  validates :borrower, presence: true

  def make_payment(value)
    remainder = amount - value
    update_attribute(:amount, remainder)
    return remainder
  end
end

我可以使用它从原始贷款金额中正确扣除一个值，但我似乎无法使用视图和表单使其工作。目前我的看法如下：

app/views/loans/show.html.erb

<p id="notice"><%= notice %></p>

<div class="row">
  <div class="col-md-2">
    <ul>
      <li><strong>Lender</strong>: <%= @loan.lender.username %></li>
      <li><strong>Borrower</strong>: <%= @loan.borrower.username %></li>
      <li><strong>Amount Remaining</strong>: <%= @loan.amount %></li>
    </ul>
    <section>
      <div class="col-md-6 col-md-offset-3">
        <%= form_for @loan do |f| %>

          <%= f.label :make_payment %>  <!--confusion -->
          <%= f.number_field :value, class: 'form-control' %>  <!--confusion -->

          <%= f.submit "Submit Payment", class: "btn btn-primary" %>
        <% end %>
      </div>
    </section>
  </div>
</div>

<%= link_to 'Edit', edit_loan_path(@loan) %> |
<%= link_to 'Back', loans_path %>

当我尝试访问该页面时，我收到一个错误wrong number of arguments (0 for 1)，这完全有道理，但我希望表单中提交的值是函数make_payment(value) 的参数（值）。我应该使用form_for @loan.make_payment do |f| 还是完全使用其他东西？我确定这是一个简单的解决方法，但我似乎无法找到我正在寻找的答案。

Answer 1

一个不错的 RESTful 解决方案可能如下所示：

resources :loans, shallow: :true do
  resources :payments, only: :create
end

---

class PaymentsController < ApplicationController

  # POST /loans/:loan_id/payments
  def create
    @loan = Loan.find(params[:loan_id])
    @loan.make_payment(payment)
    if @load.save
      redirect_to @loan, notice: "Payment successful"
    else
      redirect_to @loan, alert: "Payment count not be processed"
    end 
  end

  private 

  def payment
    require(:loan).require(:payment)[:payment]
  end
end 

然后您的表单将如下所示：

<%= form_for @loan, url: loan_payments_path(loan: @loan), method: :post do |f| %>
  <%= f.label :payment %>
  <%= f.number_field :payment, class: 'form-control' %>
  <%= f.submit "Submit Payment", class: "btn btn-primary" %>
<% end %>