如何在Rails中创建新记录之前检查现有记录？

Question

recruitment表在attendance之间具有一对多关联project_site表在“出勤”之间具有一对多关联。

在创建新的attendance记录之前，我想检查是否存在任何记录。如果存在，我想显示attendance.status否则我想显示表单代码以设置状态。我怎么用下面的代码做到这一点-

attendance_controller.rb

  def new
    @attendance = Attendance.new
    @recruitment = Recruitment.all
  end

  def create
    @attendance = Attendance.new(attendance_params)

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

_ form.html.erb

    <table>
      <thead>
        <tr>
          <th>Name</th>

          <% (1..(Time.days_in_month @project_site.attendance_month.strftime("%m").to_i)).each do |date| %>
                <th><%= date %></th>
          <% end %>

        </tr>
      </thead>

      <tbody>
        <% @recruitment.where(location: @project_site.site_id).each do |recruitment| %>
          <tr>
              <td><%= recruitment.name %></td>

              <% (1..(Time.days_in_month @project_site.attendance_month.strftime("%m").to_i)).each do |date| %>
                    <td>


                      <%= form_with(model: attendance, :html => {:id => 'attendance-form-validation'}, url:[@project_site, @attendance], local: true) do |f| %>


                          <div>
                            <div class="wrapper-class">
                              <%= f.select :status, [['P', 1], ['A', 2], ['H', 3]], {}, { onchange: 'this.form.submit()', class: 'attendance-select-input' } %>
                            </div>

                            <div>
                              <%= f.hidden_field :attendance_date, value: (@project_site.attendance_month.strftime("%Y-%m")+"-"+date.to_s)%>
                            </div>

                              <%=f.hidden_field :recruitment_id, value: recruitment.id%>

                              <%=f.hidden_field :project_site_id, value: @project_site.id%>
                            </div>

                      <% end %>
                    </td>
              <% end %>

          </tr>
        <% end %>
      </tbody>
    </table>

我尝试过-

<% if @attendance.status != nil %>
<% else %>
 <%# render form code %>
<% end %>

这对我不起作用。

Answer 1

obj = Attendance.find_or_create(attendance_id) 
if !obj.status.nil? ?
   @attendance = obj.status :
   obj.update(attendance_params) 

注意：

# find_or_create can expand to search by custom field
# This either finds an object by that id or creates a new skeleton of that object. (Just the id and the rest nil)
# Find the object in question, if the object in question's status is nil update the skeleton Attendance object with new data, else leave current data
# The .update might be .update_attributes since it's Rails 5