Ruby on rails RubyonRails：未定义的方法'model_name'；班级：班级

我试图允许用户将项目输入数据库。其中一个字段允许他们为该项目输入多种技术

这是我的项目控制器，新建和创建操作

def new
  @project = Project.new
  @all_technols = Technol.all
  @project_technol = @project.projecttechnols.build

  respond_to do |format|
    format.html # new.html.erb
    format.json { render json: @project }
  end
end

def create
  @project = Project.new(params[:project])
  params[:technols][:id].each do |technol|
    if !technol.empty?
      @project.projecttechnols.build(:technol_id => technol)
    end
  end
end

这是我的多选择技术下拉列表的新项目视图

<%= fields_for(@project_technol) do |ab| %>
  <div class="tech">
    <%= ab.label "All Tech" %><br/>
    <%= collection_select(:technols, :id, @all_technols, :id, :tech, {}, {:multiple => true} ) %>
  </div>
<% end %>

到

我现在得到这个错误：

NoMethodError in Projects#create

undefined method `map' for nil:NilClass

Extracted source (around line #240):

237: <div class="tech">
238: <%= ab.label "All Tech" %><br/>
239: 
240: <%= collection_select(:technols, :id, @all_technols, :id, :tech, {}, {:multiple => true} ) %>
241: </div>
242: <% end %>

NoMethodError在项目中#创建
nil:NilClass的未定义方法“map”
提取的源（第240行附近）：
237: 
238:

239: 
240：对}）%%>
241: 
242: 

编辑2

@all_technols=创建操作中的Technol.all

我现在得到这个错误

Showing /home/james/Desktop/webapp/app/views/projects/new.html.erb where line #233 raised:

    undefined method `model_name' for NilClass:Class

Extracted source (around line #233):

233: <%= fields_for(@project_technol) do |ab| %>
234: 
235: <div class="tech">
236: <%= ab.label "All Tech" %><br/>

NoMethodError in Projects#show

Showing /home/james/Desktop/webapp/app/views/projects/show.html.erb where line #181 raised:

undefined method `technol' for #<Project:0xb36823c>
Extracted source (around line #181):

178: <h3>Related books</h3>
179: 
180: <ul>
181:   <% @project.technol.each do |technol| %>
182:     <li><%= technol.tech %> <%= link_to "Details", technol_path(technol) %></li>
183:   <% end %>
184: </ul>

项目中的命名错误#显示
显示/home/james/Desktop/webapp/app/views/projects/show.html.erb，其中第181行出现：
未定义的方法“technol”#
提取的源（第181行附近）：
178：相关书籍
179: 
180:

181:   
182:

183:   
184:

您的

创建

操作将再次呈现

新的

视图。但是，

@project\u technol

未在

创建

操作中定义。

方法的
fields\u对传入的参数（
@project\u technol
）调用
model\u name
方法，但由于
@project\u technol=nil
，因此抛出了该错误。要解决此问题，请在
create
操作中更改

到

@JamesMcL13我猜新问题与旧问题完全相同，因为您没有在
创建
操作中设置
@all\u technols=Technol.all
。谢谢各位，我现在有一个新错误。我在项目控制器的创建操作中设置了
@all\u technols=Technol.all
。请参见edit2try
@project.technols。请改为查看每个
。谢谢。该项目现在显示在项目创建页面上选择的所有技术
Showing /home/james/Desktop/webapp/app/views/projects/new.html.erb where line #233 raised:

    undefined method `model_name' for NilClass:Class

Extracted source (around line #233):

233: <%= fields_for(@project_technol) do |ab| %>
234: 
235: <div class="tech">
236: <%= ab.label "All Tech" %><br/>

@project.projecttechnols.build(:technol_id => technol)

@project_technol = @project.projecttechnols.build(:technol_id => technol)

NoMethodError in Projects#create

undefined method `map' for nil:NilClass

Extracted source (around line #240):

237: <div class="tech">
238: <%= ab.label "All Tech" %><br/>
239: 
240: <%= collection_select(:technols, :id, @all_technols, :id, :tech, {}, {:multiple => true} ) %>
241: </div>
242: <% end %>

NoMethodError in Projects#show

Showing /home/james/Desktop/webapp/app/views/projects/show.html.erb where line #181 raised:

undefined method `technol' for #<Project:0xb36823c>
Extracted source (around line #181):

178: <h3>Related books</h3>
179: 
180: <ul>
181:   <% @project.technol.each do |technol| %>
182:     <li><%= technol.tech %> <%= link_to "Details", technol_path(technol) %></li>
183:   <% end %>
184: </ul>

@project.projecttechnols.build(:technol_id => technol)

@project_technol = @project.projecttechnols.build(:technol_id => technol)