Rails 4 form_for双重嵌套注释

Question

首先，我已经找到了一些非常有帮助的答案（请参阅下面的链接），但我仍然努力做到这一点。我没有长时间的编程，而且这绝对是我舒服自称理解的东西。

我有三种模式。举例来说，我会称它们为树，树皮，雕刻（评论）。我正在尝试为用户添加一个简单的表单部分以提交新评论（雕刻）。

的下面设置是制造误差：

NoMethodError在/树木/ 1 未定义的方法`树”的零：NilClass

控制器

class TreesController < ApplicationController 
    def show 
    @barks = Bark.where(tree_id: @tree.id) 
    @engraving= Engraving.new(:bark=> @bark) 
    end 
end 

class BarksController < ApplicationController 
    def show 
    @engravin= Engraving.new(:bark=> @bark) 
    @engravings = Engraving.where(bark_id: @bark.id) 
    end 
end 

class EngravingsController < ApplicationController 
    def show 
    @bark= Bark.find(params[:bark_id]) 
    @engraving = Engraving.new(params[:engraving]) 
    end 
end 

def create 
@bark = Bark.find(params[:bark_id]) 
@engraving = Engraving.new(params[:engraving]) 
@engraving.user_id = current_user.id 


respond_to do |format| 
    if @engraving.save 
    format.html { redirect_to tree_bark_path(@tree, @bark), notice: 'Comment was  successfully created.' } 
    format.json { render action: 'show', status: :created, location: @engraving} 
    else 
    format.html { render action: 'new' } 
    format.json { render json: @engraving.errors, status: :unprocessable_entity } 
    end 
end 

端

模型

class Tree < ActiveRecord::Base 
    belongs_to :user 
    has_many :barks 
    has_many :engravings, through: :barks 
end 

class Bark< ActiveRecord::Base 
    belongs_to :user 
    belongs_to :tree 
    has_many :engravings 

    delegate :title, :link, :to => :tree, :prefix => true 

    def new_engraving_path 
    Rails.application.routes.url_helpers.new_tree_bark_engraving_path(book, self) 
    end 

    def serializable_hash(*args) 
    super.merge 'new_engraving_path' => new_engraving_path 
    end 
end 

class Engraving< ActiveRecord::Base 
    belongs_to :user 
    belongs_to :bark 

    delegate :tree, :to => :bark, :prefix => true 

    def to_edit_path 
    Rails.application.routes.url_helpers.edit_tree_bark_engraving_path bark_tree, bark, self 
    end 

    def to_path 
    Rails.application.routes.url_helpers.tree_bark_engraving_path bark_tree, bark, self 
    end 

    def serializable_hash(*args) 
    super.merge 'path' => to_path, 'edit_path' => to_edit_path 
    end 
end 

在视图中调用窗体

在树显示页面上，我将所有树皮填充到那里。点击一个Bark元素打开一个模式，显示Bark.content和Engravings。在最后的雕刻下，我想要一个text_area表单来创建一个新的雕刻，并将其添加到这片“树皮”中。

# trees\show.html.erb 
<%= render @barks %> 

# barks\_bark.html.erb 
<%= render partial: 'barks/modal', locals: { bark: bark} %> 

# barks\modal.html.erb 
<% render partial: '/engravings/simpleForm', :collection => bark.engravings %> 

# Form partial 

    <%= form_for @engraving, :url => (new_tree_bark_engraving_path(:tree_id => @bark.tree, :bark_id => @bark.id)) do |f| %> 
    <%= f.hidden_field :bark_id %> 

    <div class="field"> 
     <%= f.text_area :content %> 
    </div> 

    <div class="actions"> 
     <%= f.submit %> 
    </div> 
    <% end %> 

路线

get "pages/home" 

    resources :trees do 
     collection do 
     get 'search' 
     post 'load_from_api' 
     end 
    resources :barks do 
     resources :engravings 
    end 
    end 
    resources :barks do 
     resources :engravings 
    end 

    root "trees#index" 

---

对方的回答来源

Rails Routing Error for nested form_for

Twice Nested Resource Form_For Issue

form_for with nested resources

Answer 1

您的错误消息NoMethodError at /trees/1 undefined method 'tree' for nil:NilClass意味着某处您必须致电.tree对象nil。我能看到发生的唯一情况是部分形式。我假设@bark.tree失败。

从你的问题，你不清楚你是从哪个控制器渲染的部分，但最可能的原因是@bark没有被传递到窗体。请确保您传递@bark到您的部分，这里有一个例子：

<%= render partial: "form", locals: {bark: @bark} %> 

Answer 2

你在你的trees#show action definining @barks，但从来没有@bark

def show @barks = Bark.where(tree_id: @tree.id) @engraving= Engraving.new(:bark=> @bark) end

所以@bark为零。