Ruby on rails 计算每月总数

你好，我正在创建一个小应用程序来帮助我管理我的信用卡

我有一个用户模型和一个信用卡模型

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  has_many :credit_cards
end

class CreditCard < ApplicationRecord
  belongs_to :user
  def credit_available
    limit - balance
  end

  def annual_interest
    if self.balance && self.interestRate
      self.balance * self.interestRate
    else
      "0.0".to_d
    end
  end


  def minimum_payment
    n = balance / 100
    b = n * 1
    i = balance * interestRate
    c = i / 12

    c + b
  end

end

景色是这样的

<% if user_signed_in? %>
  <h1>Credit Cards</h1>

  <% if current_user.credit_cards.any? %>
    <table class="mdl-data-table mdl-js-data-table">
      <thead>
        <tr>
          <th class="mdl-data-table__cell--non-numeric"><%= link_to 'Name', :sort => 'card_NickName'  %>  </th>
          <th class="mdl-data-table__cell--non-numeric"><%= link_to 'Provider', :sort => 'card_provider' %></th>
          <th class="mdl-data-table__cell--non-numeric"><%= link_to 'Points', :sort => 'points_provider'   %></th>
          <th>%</th>
          <th>Balance</th>
          <th>Limit</th>
          <th>Available</th>
          <th>Min Payments</th>
          <th colspan="3"></th>
        </tr>
      </thead>

      <tbody>
        <% @credit_cards.each do |credit_card| %>
          <tr>
            <td class="mdl-data-table__cell--non-numeric"><%= link_to credit_card.nickName, credit_card %></td>
            <td class="mdl-data-table__cell--non-numeric"><%= credit_card.provider %></td>
            <td class="mdl-data-table__cell--non-numeric"><%= credit_card.pointsProvidor %></td>
            <td><%= number_to_percentage(credit_card.interestRate * 100, precision: 2) %></td>
            <td><%= number_to_currency(credit_card.balance, unit: "$") %></td>
            <td><%= number_to_currency(credit_card.limit, unit: "$") %></td>
            <td><%= number_to_currency(credit_card.credit_available, unit: "$") %></td>
            <td><%= number_to_currency(credit_card.minimum_payment, unit: "$") %></td>
            <td></td>
            <td></td>
            <td></td>
          </tr>
        <% end %>
      </tbody>
      <tfoot>
        <tr>
          <td></td>
          <td></td>
          <td></td>
          <td></td>
          <td><%= number_to_currency(@credit_card_debt, unit: "$") %></td>
          <td><%= number_to_currency(@credit_limit, unit: "$") %></td>
          <td><%= number_to_currency(@available_credit, unit: "$") %></td>
          <td><%= @total_monthly_payment %></td>
          <td></td>
          <td></td>
          <td></td>
        </tr>
      </tfoot>
    </table>

    <br>

    <%= link_to new_credit_card_path, class: 'mdl-button mdl-js-button mdl-button--fab mdl-button--colored' do %>
            <i class="material-icons">add</i>
        <% end %>
  <% else %>
    You have no Credit Cards, better
    <%= link_to new_credit_card_path, class: 'mdl-button mdl-js-button mdl-button--fab mdl-button--colored' do %>
      <i class="material-icons">add</i>
    <% end %>
    one.
  <% end %>
<% else %>

  <div class="mdl-cell mdl-cell--2-col mdl-cell--2-col-tablet"></div>
  <div class="mdl-cell mdl-cell--8-col mdl-cell--8-col-tablet"><h1>Credit Card Smarts at your fingertips</h1></div>
  <div class="mdl-cell mdl-cell--2-col mdl-cell--2-col-tablet"></div>
<% end %>

信用卡
'卡片\u昵称'%>
'卡\u提供程序'%>
'点\提供程序'%>
%
平衡
极限
可用
最低付款额


添加
你最好没有信用卡
添加
一个。
触手可及的信用卡智能

在我尝试计算@total_monthly_付款时出现以下错误之前，一切都很好

NameError in CreditCardsController#index
undefined local variable or method `balance' for #<CreditCardsController:0x00007fc18f7dfa48>
Extracted source (around line #5):
3
4
5
6
7
8


  def minimum_payment
    n = balance / 100
    b = n * 1
    i = balance * interestRate
    c = i / 12

CreditCardsController索引中的

name错误
未定义的局部变量或方法“balance”#
提取的源（第5行附近）：
3.
4.
5.
6.
7.
8.
def最低付款额
n=余额/100
b=n*1
i=余额*利率
c=i/12

控制器

class CreditCardsController < ApplicationController
  before_action :authenticate_user!
  before_action :set_credit_card, only: [:show, :edit, :update, :destroy]

  # GET /credit_cards
  # GET /credit_cards.json
  def index
    @credit_cards = current_user.credit_cards
    @credit_card_debt = current_user.credit_cards.sum(:balance)
    @credit_limit = current_user.credit_cards.sum(:limit)
    @available_credit = current_user.credit_cards.sum(:limit) - current_user.credit_cards.sum(:balance)
    @total_monthly_payment = total_monthly_payment
  end



  # GET /credit_cards/1
  # GET /credit_cards/1.json
  def show
  end

  # GET /credit_cards/new
  def new
    @credit_card = current_user.credit_cards.build
  end

  # GET /credit_cards/1/edit
  def edit
  end

  # POST /credit_cards
  # POST /credit_cards.json
  def create
    @credit_card = current_user.credit_cards.new(credit_card_params)

    respond_to do |format|
      if @credit_card.save
        format.html { redirect_to @credit_card, notice: 'Credit card was successfully created.' }
        format.json { render :show, status: :created, location: @credit_card }
      else
        format.html { render :new }
        format.json { render json: @credit_card.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /credit_cards/1
  # PATCH/PUT /credit_cards/1.json
  def update
    respond_to do |format|
      if @credit_card.update(credit_card_params)
        format.html { redirect_to @credit_card, notice: 'Credit card was successfully updated.' }
        format.json { render :show, status: :ok, location: @credit_card }
      else
        format.html { render :edit }
        format.json { render json: @credit_card.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /credit_cards/1
  # DELETE /credit_cards/1.json
  def destroy
    @credit_card.destroy
    respond_to do |format|
      format.html { redirect_to credit_cards_url, notice: 'Credit card was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
  # Use callbacks to share common setup or constraints between actions.
  def set_credit_card
    @credit_card = CreditCard.find(params[:id])
  end

  # Never trust parameters from the scary internet, only allow the white list through.
  def credit_card_params
    params.require(:credit_card).permit(:nickName, :provider, :pointsProvidor, :interestRate, :balance, :limit, :user_id )
  end
end

class CreditCardsController

---

请帮忙

以以下方式修改模型方法：

def total_monthly_payment
    n = current_user.credit_cards.sum(&:minimum_payment)
end

只是一个旁注：-

n = current_user.credit_cards.sum(&:minimum_payment)

首先，它将获得所有信用卡最低付款的数组，然后 这将一个接一个地迭代这个数组，并在其中循环。因此，对于100或1000条记录，这不是一种有效的方法

为此，应使用sql查询：-

n = current_user.credit_cards.sum(:minimum_payment)

这将只触发sql查询，有些类似于：-

---

从

信用卡

中选择总和（

信用卡

最低付款

），请添加控制器的索引操作。@razvans已添加，但在我可以之前已由其他人完成。。。。我不认为这有多大的不同，但谢谢现在有人应该能够得到一个完整的答案。你能解释一下-：&意味着你正在通过一个街区以备将来参考吗

n = current_user.credit_cards.sum(:minimum_payment)