我收到此错误：“'3' 不是 ActiveModel 兼容的对象。它必须实现：to_partial_path。”只有当我添加验证时才会发生

Question

这是我得到的错误。

这是我的模型代码。

class Subject < ActiveRecord::Base
  has_many :pages

  validates :name,
  :presence => true,
  :length => { :maximum => 255 }


  scope :visible, lambda { where(:visible => true) }
  scope :invisible, lambda { where(:visible => false) }
  scope :sorted, lambda { order("subjects.position ASC")}
  scope :newest_first, lambda { order("subject.created_at DESC") }
  scope :search, lambda { |query|
    where(["name LIKE ?", "%#{query}%"])
  }
end

我注意到它在说明我的创建操作。所以是这样的：

class SubjectsController < ApplicationController

    layout "admin"

  def index
    @subjects = Subject.sorted  
  end

  def show
    @subject = Subject.find(params[:id])
  end

  def new
    @subject = Subject.new({:name => 'Default'})
    @subject_count = Subject.count + 1
  end

  def create
    # Instantiate a new object using form parameters
    @subject = Subject.new(subject_params)
    # Save the object
    if @subject.save
        # If save succeeds, redirect to the index
        flash[:notice] = "The subject was created successfully."
        redirect_to(:action => 'index')
      else
        @subject_count = Subject.count + 1
        render(new)
    end
  end

  def edit
    @subject = Subject.find(params[:id])
    @subject_count = Subject.count
  end

  def update
    # Find an existing object using form parameters
    @subject = Subject.find(params[:id])
    # Update the object
    if @subject.update_attributes(subject_params)
        # If save succeeds, redirect to the show
        flash[:notice] = "The subject was updated successfully."
        redirect_to(:action => 'show', :id => @subject.id)
      else 
        # If update fails, redisplay the form so user can fix problem.
        @subject_count = Subject.count
        render('edit')
    end
  end

  def delete
   @subject = Subject.find(params[:id])
  end

  def destroy
    subject = Subject.find(params[:id]).destroy
    flash[:notice] = "The subject '#{subject.name}' was deleted successfully."
    redirect_to(:action => 'index')
  end

  private

    def subject_params
      # same as using "params[:subject]", except that it:
      # -raises an error if :subject is not present
      # -allows listed attributes to be mass-assigned
      params.require(:subject).permit(:name, :position, :visible)
    end

end

如果我取消验证，它可以工作，但是我可以创建没有名称的主题。我注意到如果我添加一个主题，括号“3”中的数字会向上移动。我想知道它是否与选择表单有关。表格如下：

    <%= error_messages_for(@subject) %>

<table summary="Subject form fields" class="table table-hover">
    <tr>
        <th><%= f.label(:name, "Name") %></th>
        <td><%= f.text_field(:name) %></td>
    </tr>
    <tr>
        <th><%= f.label(:position) %></th>
        <td><%= f.select(:position, 1..@subject_count) %></td>
    </tr>
    <tr>
        <th><%= f.label(:visible) %></th>
        <td><%= f.check_box(:visible) %></td>
    </tr>
</table>

更新：我正在为每个请求添加索引视图。

<% @page_title = 'Subjects' %>

<div class="subjects show">

    <h2>Subjects</h2>

    <%= link_to("Add New Subject", {:action => 'new'}, :class => 'action new btn btn-default') %>

    <table class="listing table table-hover" summary="Subject list">
        <tr class="header">
            <th>Position</th>
            <th>Subject</th>
            <th>Visible</th>
            <th>Pages</th>
            <th>Actions</th>
        </tr>
        <% @subjects.each do |subject| %>
        <tr>
            <td><%= subject.position %></td>
            <td><%= subject.name %></td>
            <td class="center"><%= subject.visible ? 'Yes' : 'No' %></td>
            <td class="center"><%= subject.pages.size %></td>
            <td class="actions">
                <%= link_to("Show", {:action => 'show', :id => subject.id}, :class => 'action show') %>
                <%= link_to("Edit", {:action => 'edit', :id => subject.id}, :class => 'action edit') %>
                <%= link_to("Delete", {:action => 'delete', :id => subject.id}, :class => 'action delete') %>
            </td>
        </tr>
        <% end %>
    </table>
</div>

Answer 1

由于 create 操作的 else 部分的语法错误，活动模型抛出异常（http://apidock.com/rails/v3.2.1/ActionView/PartialRenderer/partial_path）

def create
   #few lines escaped....
  else
    @subject_count = Subject.count + 1
    render(new) # <-- Error
end

它应该是render :new 或render 'new'，如Nobilik 所述。您的方法应如下所示：

def create
   #few lines escaped....
  else
    @subject_count = Subject.count + 1
    render :new # for best practice
end