如何解决未初始化的常量搜索::错误

我正在为与汽车维护相关的约会模型创建一个高级搜索/过滤器，其中每个 schema.rb 中的表是：

  create_table "appointments", force: :cascade do |t|
    t.string "VIN"
    t.string "owner_email"
    t.string "date"
    t.string "time"
    t.string "reason"
    t.string "parts_needed"
    t.string "hours_needed"
    t.string "cost"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "searches", force: :cascade do |t|
    t.string "VIN"
    t.string "email"
    t.string "after_date"
    t.string "before_date"
    t.string "time"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

在我的 search.rb 模型中，我定义了搜索功能：

class Search < ApplicationRecord

    def search_appointments
        appointments = Appointment.all
        # appointments = appointments.where("VIN LIKE ?", VIN) if VIN.present? GIVES ERROR
        appointments = appointments.where("owner_email LIKE ?", email) if email.present?
        appointments = appointments.where("date >= ?", after_date) if after_date.present?
        appointments = appointments.where("date <= ?", before_date) if before_date.present?
        if !time=="Any"
            appointments = appointments.where("time LIKE ?", time) if time.present?
        end

        return appointments
    end
end

然后在我的 show.html.erb 中显示结果过滤器：

<h2 align="center">Search Results</h2>
</br>


<div class="container-fluid">
    <% if @search.search_appointments.empty? %>
        <p> No Appointments Fit This Search</p>

    <% else %>
        <%= @search.search_appointments.each do |a| %>

        Email: <%= a.owner_email%> </br>
        Date: <%= a.date%> </br>
        Time: <%= a.time%> </br>
        VIN: <%= a.VIN %> </br>

        </br>
        </br>
        </br>
        <% end %>
    <% end %>
    </br>
    <%= link_to 'Return', @search, method: :delete %>
</div>

一切正常，除了 search.rb 模型中的第一次过滤尝试，该行被注释掉。如果我取消注释该行并运行搜索，则会突出显示该行并出现错误：

uninitialized constant Search::VIN

我不明白为什么会发生这种情况，因为所有其他过滤器都可以正常工作。我将不胜感激任何建议，谢谢。

搜索控制器：

class SearchesController < ApplicationController

    def new
        @search = Search.new
    end

    def create
        @search = Search.create(search_params)
        redirect_to @search
    end

    def show
        @search = Search.find(params[:id])
    end

    def destroy
        @search = Search.find(params[:id])
        @search.destroy

        redirect_to admin_path
    end

    def search_params
        params.require(:search).permit(:VIN, :email, :after_date, :before_date, :time)
    end
end

我的“新”页面是一个表单，用户在其中填写过滤器参数，然后单击提交按钮将它们带到列出过滤约会的显示页面。