Question

所以if语句有点问题，我的数据库结构像这样

所以我要检查布尔值是对还是错，这就是我目前正在尝试执行的语句

<% if @course_modules_users.where(complete: true).nil? %>
  <i class="fas fa-check text-green float-left mr-1"></i>
  <span class="text-xs mr-2">Completed</span>
<% else %>
  <%= link_to complete_course_module_path(course_module.id), method: :put do %>
    <i class="fas fa-check text-grey-darkest float-left mr-2"></i>
  <% end %>
<% end %>

但是我只是看到这个

编辑＃1

我可以做这样的事情

<% if @course_modules_users.where(complete: true) %>

但是两个刻度都完成了

但是正如您在数据库中看到的那样，只有一个是正确的。

编辑＃2

course_modules_users

模型

class CourseModulesUser < ApplicationRecord
  belongs_to :course_module
  belongs_to :courses_user

  after_update :update_courses_user, if: :completed?

  def siblings
    self.class.where(courses_user_id: self.courses_user_id)
  end

  def completed!
    self.update_attributes(complete: true)
  end

  def completed?
    siblings.all?(&:complete?)
  end

  def update_courses_user
    self.courses_user.completed!
  end
end

CoursesController显示方法

def show
  course = Course.friendly.find(params[:id])
  @course_modules = course.course_modules.order(created_at: :asc)
  @course_modules_users = CourseModulesUser.all
end

希望有帮助。

编辑＃3

显示

<% if user_signed_in? %>
  <section class="pt-4 px-8">
    <section class="flex flex-wrap justify-between">
      <h3 class="font-normal text-grey-dark mb-4 py-2">
        <% if current_user.isAdmin? %>
          <%= @course.title %>
        <% else %>
          <%= @course.title %> Modules
        <% end %>
      </h3>
      <%= render 'layouts/dashboard/account' %>
    </section>
  </section>

  <section class="px-8">
    <% if Order.exists?(user_id: current_user.id, course_id: @course.id) %>
      <% @course_modules.each do |course_module| %>
        <section class="accordion-toggle">
          <section class="w-full sm:pr-4 pb-4">
            <section class="rounded shadow bg-grey-lighter border-b">
              <section class="flex justify-between px-6 p-4">
                <section class="flex items-center px-6 text-grey-darker">
                  <section class="font-bold text-base">
                    <%= course_module.title %>
                  </section>
                </section>

                <section class="flex items-center">
                  <% if user_signed_in? %>
                    <% if current_user.isAdmin? %>
                      <%= link_to "Edit", edit_course_module_path(course_module), class: "text-base text-grey-dark hover:text-darker px-4 py-2 border-2 border-grey leading-none no-underline hover:border-2 hover:border-grey-dark" %>
                    <% else %>
                      <% @course_modules_users.each do |cmu| %>
                        <% if cmu.complete == true %>
                          <i class="fas fa-check text-green float-left mr-1"></i>
                          <span class="text-xs mr-2">Completed</span>
                        <% else %>
                          <%= link_to complete_course_module_path(course_module.id), method: :put do %>
                            <i class="fas fa-check text-grey-darkest float-left mr-2"></i>
                          <% end %>
                        <% end %>
                      <% end %>
                      <i class="flex items-center fal fa-angle-up"></i>
                    <% end %>
                  <% end %>
                </section>
              </section>
            </section>

            <section class="accordion-items hidden">
              <% course_module.course_exercises.each do |exercise| %>
                <section class="w-full">
                  <section class="rounded shadow bg-grey-lighter border-b">
                    <section class="flex justify-between px-6 p-4">
                      <section class="flex items-center px-6 text-grey-darker">
                        <section class="font-bold text-base pl-4">
                          - <%= exercise.title %>
                        </section>
                      </section>

                      <section>
                        <% if user_signed_in? %>
                          <% if current_user.isAdmin? %>
                            <%= link_to "Edit", edit_course_exercise_path(exercise), class: "text-base text-grey-dark hover:text-darker px-4 py-2 border-2 border-grey leading-none no-underline hover:border-2 hover:border-grey-dark" %>
                          <% else %>
                            <%= link_to "View Exercise", exercise, class: "text-base text-grey-dark hover:text-darker px-4 py-2 border-2 border-grey leading-none no-underline hover:border-2 hover:border-grey-dark" %>
                          <% end %>
                        <% end %>
                      </section>
                    </section>
                  </section>
                </section>
              <% end %>
            </section>
          </section>
        </section>
      <% end %>
    <% else %>
      <h3>You have not bought this course!</h3>

      <%= form_with(url: '/payments/create') do |f| %>
        <%= render partial: "stripe_checkout_button" %>
        <%= hidden_field_tag(:course_id, @course.id) %>

        <%= f.submit "Buy this course", class: "bg-blue hover:bg-blue-dark text-white font-semibold py-3 px-4 border-2 rounded-sm border-blue-dark shadow outline-none" %>
      <% end %>
  <% end %>
  </section>
<% else %>
  <section class="flex h-64 hero-banner p-4">
    <section class="flex items-center mx-auto">
      <h2 class="uppercase">
        <%= @course.title %>
      </h2>
    </section>
  </section>

  <section class="pt-4 px-4">
    <section class="w-full">
      <section class="rounded overflow-hidden shadow">
        <section style="padding: 56.25% 0 0 0; position: relative;">
          <iframe src="https://player.vimeo.com/video/<%= @course.trailer %>" style="position: absolute; top: 0; left: 0; width: 100%; height: 100%;" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
        </section>
      </section>
    </section>

    <section class="flex flex-wrap -mx-4">
      <section class="w-full lg:w-3/4 p-4">
        <section class="bg-grey-lightest shadow text-grey-darker p-4">
          <h2 class="font-normal mb-4">Course description</h2>
          <p class="font-normal whitespace-pre-wrap"><%= @course.description %></p>
        </section>
      </section>
      <section class="w-full lg:w-1/4 p-4">
        <section class="bg-grey-lightest shadow text-grey-darker p-4 mb-4">
          <h3 class="font-normal mb-4">Course Price</h3>
          <p class="font-bold text-3xl text-green">£<%= @course.price %></p>
        </section>

        <%= link_to "Sign up to purchase", new_user_registration_path, class: "bg-blue hover:bg-blue-dark text-white font-semibold py-3 px-4 border-2 rounded-sm border-blue-dark shadow outline-none no-underline" %>

        <section class="bg-grey-lightest shadow text-grey-darker py-4 px-4 mt-4">
          <h3 class="font-normal mb-4">Course Modules</h3>
            <% @course_modules.each do |course_module| %>
              <section class="py-2 border-b-2 border-light modules">
                <%= course_module.title %>
              </section>
          <% end %>
        </section>
      </section>
    </section>
  </section>
<% end %>

Answer 1

@course_modules_users.where(complete: true)将返回 Array 。

[]和nil是不同的概念。 [] != nil; [].nil? == false。

在红宝石中，除nil和false以外的所有东西都被认为是“真实的”。例如，这意味着[]是一个“真实的”值。

将这些知识放在一起可以解释您在上面看到的所有内容：

<% if @course_modules_users.where(complete: true).nil? %>

这将永远不会发生，因为该查询的结果不是nil；这是一个（可能是空的）数组。

<% if @course_modules_users.where(complete: true) %>

这将总是发生，因为任何Array（甚至是一个空的）在红宝石中都是“真实的”。

您可以通过多种方式来编写此代码，例如：

<% if @course_modules_users.where(complete: true).empty? %>

或者：

<% if @course_modules_users.where(complete: true).none? %>

无法检查布尔值是否存在Rails 5

1 个答案: