Ruby on rails RubyonRails创建记录时遇到的问题有很多：通过关系

我正在使用rails 3.2.14，第一次在使用has_many:through时遇到问题。我正在使用一个has_many：通过图像和设计表之间的关系，使用一个Design_Pictures表来存储设计图像的顺序排序。所有图像都与一个用户关联。稍后，我希望能够灵活地在images表中存储与特定设计无关的其他图像

我可以成功地将示例数据添加到数据库中，并在我的show design页面中显示图像标题（存储在images表中）和排名（存储在design_pictures表中）。我搞不懂的是如何创建一个新的设计图片。一旦我可以得到这个工作，我将使用CarrierWave或回形针添加图像到图像表

以下是我的模型：

app/models/image.rb:

class Image < ActiveRecord::Base
  attr_accessible :title
  belongs_to :user
  has_many :design_pictures, dependent: :destroy 
  has_many :designs, :through => :design_pictures

  validates :user_id, presence: true
  validates :title, length: { maximum: 80 }
end

class Design < ActiveRecord::Base
  attr_accessible :title
  has_many :design_pictures, dependent: :destroy 
  has_many :images, :through => :design_pictures

  validates :title, presence: true, length: { maximum: 60 }
end

class DesignPicture < ActiveRecord::Base
  attr_accessible :ranking
  belongs_to :image
  belongs_to :design

  validates :image_id, presence: true
  validates :design_id, presence: true   

  default_scope order: 'design_pictures.ranking ASC'
end

class User < ActiveRecord::Base
  attr_accessible :name
  has_many :designs, dependent: :destroy 
  has_many :images, dependent: :destroy

  validates :name, presence: true, length: { maximum: 50 }
end

            <div>
                <% if @design.design_pictures.any? %>
                    <h3>Images (<%= @design.design_pictures.count %>)</h3>
                    <ul>
                        <%= render @design_pictures %>
                    </ul>
                <% end %>
            </div>

            <div>
                <%= render 'shared/design_picture_form' %>
            </div>

<%= form_for(@design_picture) do |f| %>
    <%= render 'shared/error_messages', object: f.object %>

    <%= f.label :title, "Title" %>
    <%= f.text_field :title, 
                placeholder: "Name your image.",
                class: "" %>

    <%= f.label :ranking, "Ranking" %>
    <%= f.text_field :ranking, 
            placeholder: "Rank your design picture.",
            class: "" %>            

    <%= hidden_field_tag(:design_id, @design.id) %>

    <%= f.submit "Add Image", class: "btn btn-large btn-primary" %>
<% end %>

app/controllers/design\u pictures\u controller.rb

<li>
    <%= design_picture.image.title %> - Ranking: <%= design_picture.ranking %>
</li>

    def show
        @design = Design.find(params[:id])
        @design_pictures = @design.design_pictures.find(:all, :limit => 10)

        @image = current_user.images.build 
        @design_picture = @design.design_pictures.build
    end

    def create
        @current_design = Design.find(params[:design_id])
        @image = current_user.images.new(params[:title])
        @design_picture = @current_design.design_pictures.build(:image_id => @image.id, params[:ranking])

        if @design_picture.save
            flash[:success] = "Micropost created!"
            redirect_to @current_design
        else
            redirect_to designs_url
        end
    end

<%= form_for(@design_picture) do |f| %>
<%= render 'shared/error_messages', object: f.object %>

<%= label_tag(:title, "Title") %>
<%= text_field_tag(:title) %>   

<%= f.label :ranking, "Ranking" %>
<%= f.text_field :ranking, 
        placeholder: "Rank your design picture.",
        class: "" %>            

<%= hidden_field_tag(:design_id, @design.id) %>

<%= f.submit "Add Image", class: "btn btn-large btn-primary" %>

def show
    @design = Design.find(params[:id])
    @design_pictures = @design.design_pictures.find(:all, :limit => 10)

    @design_picture = @design.design_pictures.build
end

def create
    @image = current_user.images.create(:title => params[:title])
    @current_design = Design.find(params[:design_id])       
    @design_picture = @current_design.design_pictures.build(params[:design_picture])
    @design_picture.image_id = @image.id

    if @design_picture.save
        flash[:success] = "Design Picture created!"
        redirect_to @current_design
    else
        redirect_to designs_url
    end
end

访问design_图片表单部分时出错：

undefined method `title' for #<DesignPicture image_id: nil, design_id: 1427, ranking: nil>

未定义的方法“title”#

如果我从表单中删除标题，我可以提交表单，但不会创建任何内容

---

非常感谢您的帮助。

您的

DesignPicture

没有

title

属性。当您这样做时：

@design.design_pictures.build

它构建了一个新的

DesignPicture

实例。以下情况不起作用：

<%= form_for(@design_picture) do |f| %>
  # ...

  <%= f.label :title, "Title" %>

  # ...

# ...
# ...

---

您可能想看看

我不确定这是否是最好的方法，但这就是我如何让我的表单提交并创建具有标题属性的图像条目和具有排名属性的设计图片条目的方法。我最终不需要使用accepts\u嵌套的属性

app/views/shared/\u design\u picture\u form.html.erb

<li>
    <%= design_picture.image.title %> - Ranking: <%= design_picture.ranking %>
</li>

    def show
        @design = Design.find(params[:id])
        @design_pictures = @design.design_pictures.find(:all, :limit => 10)

        @image = current_user.images.build 
        @design_picture = @design.design_pictures.build
    end

    def create
        @current_design = Design.find(params[:design_id])
        @image = current_user.images.new(params[:title])
        @design_picture = @current_design.design_pictures.build(:image_id => @image.id, params[:ranking])

        if @design_picture.save
            flash[:success] = "Micropost created!"
            redirect_to @current_design
        else
            redirect_to designs_url
        end
    end

<%= form_for(@design_picture) do |f| %>
<%= render 'shared/error_messages', object: f.object %>

<%= label_tag(:title, "Title") %>
<%= text_field_tag(:title) %>   

<%= f.label :ranking, "Ranking" %>
<%= f.text_field :ranking, 
        placeholder: "Rank your design picture.",
        class: "" %>            

<%= hidden_field_tag(:design_id, @design.id) %>

<%= f.submit "Add Image", class: "btn btn-large btn-primary" %>

def show
    @design = Design.find(params[:id])
    @design_pictures = @design.design_pictures.find(:all, :limit => 10)

    @design_picture = @design.design_pictures.build
end

def create
    @image = current_user.images.create(:title => params[:title])
    @current_design = Design.find(params[:design_id])       
    @design_picture = @current_design.design_pictures.build(params[:design_picture])
    @design_picture.image_id = @image.id

    if @design_picture.save
        flash[:success] = "Design Picture created!"
        redirect_to @current_design
    else
        redirect_to designs_url
    end
end

app/controllers/design\u pictures\u controller.rb

<li>
    <%= design_picture.image.title %> - Ranking: <%= design_picture.ranking %>
</li>

    def show
        @design = Design.find(params[:id])
        @design_pictures = @design.design_pictures.find(:all, :limit => 10)

        @image = current_user.images.build 
        @design_picture = @design.design_pictures.build
    end

    def create
        @current_design = Design.find(params[:design_id])
        @image = current_user.images.new(params[:title])
        @design_picture = @current_design.design_pictures.build(:image_id => @image.id, params[:ranking])

        if @design_picture.save
            flash[:success] = "Micropost created!"
            redirect_to @current_design
        else
            redirect_to designs_url
        end
    end

<%= form_for(@design_picture) do |f| %>
<%= render 'shared/error_messages', object: f.object %>

<%= label_tag(:title, "Title") %>
<%= text_field_tag(:title) %>   

<%= f.label :ranking, "Ranking" %>
<%= f.text_field :ranking, 
        placeholder: "Rank your design picture.",
        class: "" %>            

<%= hidden_field_tag(:design_id, @design.id) %>

<%= f.submit "Add Image", class: "btn btn-large btn-primary" %>

def show
    @design = Design.find(params[:id])
    @design_pictures = @design.design_pictures.find(:all, :limit => 10)

    @design_picture = @design.design_pictures.build
end

def create
    @image = current_user.images.create(:title => params[:title])
    @current_design = Design.find(params[:design_id])       
    @design_picture = @current_design.design_pictures.build(params[:design_picture])
    @design_picture.image_id = @image.id

    if @design_picture.save
        flash[:success] = "Design Picture created!"
        redirect_to @current_design
    else
        redirect_to designs_url
    end
end

---

由于

DesignPicture

属于

Image

，如何让它使用Image

title

属性？您可以使用

@design\u picture.design.title

访问它，感谢您指出嵌套表单。这是我问题的一部分。如果去掉title属性，它仍然不会创建任何内容。我认为我有一个更大的潜在问题，那就是我不知道如何使用has_-many:through关系创建新记录。我使用的是嵌套表单，但我认为我的控制器中有一个错误，那就是阻止它使用图像标题字段。你看到这有什么问题吗：

def show@design=design.find（params[：id]）@design\u pictures=@design.design\u pictures.find（：all，：limit=>10）@image=current\u user.images.build@design\u pictures=@design.design\u pictures.build end

没有问题，

title

属性仅存在于

@design

实例上。不在

@design\u图片上

。您可以使用

@design.respond_to？（：title）

和

@design_picture.respond_to？（：title）