代码之家 › 专栏 › 技术社区 › Steven Aguilar

在erb数组迭代上为nil:NilClass定义的未定义方法“each”

erb ruby ruby-on-rails

0

Steven Aguilar · 技术社区 · 7 年前

class CustomersController < ApplicationController
  def index
    if params[:keywords].present?
      @keywords = params[:keywords]
      customer_search_term = CustomerSearchTerm.new(@keywords)
      @customer = Customer.where(
        customer_search_term.where_clause,
        customer_search_term.where_args).
        order(customer_search_term.order)
    else
      @customers = []
    end
  end
end

如您所见,如果没有找到记录,则假设返回一个空数组,但返回一个Nil对象。

[![<header>
  <h1 class="h2">Customer Search</h1>
</header>

<section class="search-form">
  <%= form_for :customers, method: :get do |f| %>
    <div class="input-group input-group-lg">
      <%= label_tag :keywords, nil, class: "sr-only" %>
      <%= text_field_tag :keywords, nil,
                          placeholder: "First Name, Last Name or Email Address",
                          class: "form-control input-lg" %>

      <span class="input-group-btn">
        <%= submit_tag "Find Customers", class: "btn btn-primary btn-lg" %>
      </span>
    </div>
  <% end %>
</section>

<section class="search-results">
  <header>
    <h1 class="h3">Results</h1>
  </header>
  <table class="table table-striped">
    <thead>
      <tr>
        <th>First Name</th>
        <th>Last Name</th>
        <th>Email</th>
        <th>Joined</th>
      </tr>
    </thead>
    <tbody>
      <% @customers.each do |customer| %>
        <tr>
          <td><%= customer.first_name %></td>
          <td><%= customer.last_name %></td>
          <td><%= customer.email %></td>
          <td><%= l customer.created_at.to_date %></td>
        </tr>
      <% end %>
    </tbody>
  </table>
</section>][1]][1]

2 回复 | 直到 7 年前

1

max pleaner 7 年前

您应该了解的第一件事是实例变量返回 nil @fake_var == nil 如果你从未定义 @fake_var puts(fake_var) 将为fake_var提出命名错误。

现在看看你的模板。不管发生什么事情 @customers . 如果 @客户 尚未设置,您将看到一个NoMethodError,因为您无法调用 each 在…上 无

最后,看看你的控制器动作:

  def index
    if params[:keywords].present?
      @keywords = params[:keywords]
      customer_search_term = CustomerSearchTerm.new(@keywords)
      @customer = Customer.where(
        customer_search_term.where_clause,
        customer_search_term.where_args).
        order(customer_search_term.order)
    else
      @customers = []
    end
  end

params[:keywords].present? . 你从来没有设定 @客户 在这种情况下是这样的当模板尝试访问它时。

我认为如果你简单地更换 @customer = @customers = 这会解决你的问题。

2

0

Exwire 7 年前

def index
  return [] unless params[:keywords]
  @keywords = params[:keywords]
  customer_search_term = CustomerSearchTerm.new(@keywords)
  @customer = Customer.where(
    customer_search_term.where_clause,
    customer_search_term.where_args).
    order(customer_search_term.order
  ).to_a
end

https://apidock.com/ruby/Array/to_a