您好我正在创建一个小应用程序来帮助我管理我的信用卡。
我有用户模型和信用卡模型
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
如您所见，我已经计算了一个方法，包括我的credit_cards模型中的monthly_payment
现在我想每月累计信用卡付款。所以我在我的信用卡模型中添加了另一种名为total_monthly_payment的方法，该方法将current_users credit_card monthly_payments总计为总和。
def total_monthly_payment
n = current_user.credit_cards.sum(minimum_payment)
n
end
视图就像这样
<% 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 %>
一切正常，直到我得到以下错误时才尝试计算@total_monthly_payment。
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
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
请帮忙！
答案 0 :(得分：2)
以这种方式修改模型方法：
def total_monthly_payment
n = current_user.credit_cards.sum(&:minimum_payment)
end
答案 1 :(得分：1)
只是旁注： -
requireAuth首先它将获得所有credit_card的minimum_payment的数组然后 这将逐个迭代这个数组并循环遍历它。所以对于100或1000条记录来说，这是无效的方式。
为此你应该使用sql查询： -
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只会触发sql查询，有些如下： -
SELECT SUM（n = current_user.credit_cards.sum(&:minimum_payment)
。n = current_user.credit_cards.sum(:minimum_payment)
）FROM credit_cards