ruby-on-rails - has_many :through Association, NoMethodError( `each' 的未定义方法 "":String)并保存关联

Question

我无法让 has_many :through Association 工作。我是否需要在 post_controller 的创建方法中设置一些额外的东西，以保存 post_category？ (在代码下方，错误和我的尝试)

我有一个 has_many :through Association with post, post_category and as join 表分类如下:

帖子模型:

class Post < ApplicationRecord
  has_many :categorizations
  has_many :post_categories, :through => :categorizations
end

Post::Category 模型(使用命名空间以获得更好的项目结构):

class Post::Category < ApplicationRecord
  has_many :categorizations
  has_many :posts, :through => :categorizations
end

分类模型(使用类名，Post::Category 命名空间的原因):

class Categorization < ApplicationRecord
  belongs_to :post
  belongs_to :post_category, :class_name => 'Post::Category'
end

然后我在 View 中有一个选择，我在其中创建一个带有 post_category 的帖子:

<div class="form-group">
  <%= f.label :post_categories, :class => 'control-label', :value => 'Category: ' %>
  <%= f.select :post_categories, options_from_collection_for_select(all_post_categories, :id, :name), {}, {class: 'selectpicker', :'data-live-search' => 'true', required: 'false' } %>
</div>

在 posts_controller 中，我允许使用 :post_categories 符号:

def post_params
  params.require(:post).permit(:post_categories)
end

这是我的协会迁移文件:

class CreateCategorizations < ActiveRecord::Migration[5.0]
  def change
    create_table :categorizations do |t|
      t.integer :post_id
      t.integer :post_category_id

      t.timestamps
    end
    add_index :categorizations, :post_id
    add_index :categorizations, :post_category_id
    # multiple-key index enforces uniqueness on (post_id, post_category_id)
    # pairs, so that a category can't have the same post twice
    add_index :categorizations, [:post_id, :post_category_id], unique: true
  end
end

当我尝试提交表单时，我在日志中收到以下错误:

NoMethodError (undefined method `each' for "3":String):
app/controllers/posts_controller.rb:32:in `create'

所以我搜索了一些答案 ok -> You can't assign string to association .

我尝试了另一种方法让协会继续运作。

所以我尝试使用 post_category_id，就像推荐的一样 here

我在view的select里设置

<%= f.select :post_category_id, options_from_collection_for_select(all_post_categories, :id, :name), {}, {class: 'selectpicker', :'data-live-search' => 'true', required: 'false' } %>

然后在 posts_controller 中允许 category_id:

def post_params
  params.require(:post).permit(:post_category_id)
end

在 Post 模型中:

class Post < ApplicationRecord
  has_many :categorizations
  has_many :post_category_id, :through => :categorizations
end

这是新的错误:

Could not find the source association(s) "post_category_id" or :post_category_id in model Categorization. Try 'has_many :post_category_id, :through => :categorizations, :source => <name>'. Is it one of post or post_category?

好的，因为没有 post_category_id 关联。

更新:

post_params:

<ActionController::Parameters {"content"=>"content", "post_categories"=>"2"} permitted: true>

Answer 1

我用这个 answer 找到了适合我的解决方案还有这个question .

第一个只保存一个 Post::Category with Post 的解决方案

关于这个answer ，我必须将 posts_controller 中的 permit 参数更改为:

def post_params
  params.require(:post).permit(:post_category_ids)
end

然后我还需要在创建带有 post_category 的帖子的 View 中更改选择:

<div class="form-group">
  <%= f.label :post_category_ids, :class => 'control-label', :value => 'Category: ' %>
  <%= f.select :post_category_ids, options_from_collection_for_select(all_post_categories, :id, :name), {}, {class: 'selectpicker', :'data-live-search' => 'true', required: 'false' } %>
</div>

就是这样。其余代码仍然与我在第二次尝试我的问题之前展示的相同。

用一个帖子保存多个 Post::Category 的第二种解决方案

关于这个question ，我需要将 posts_controller 中的 permit 参数更改为:

def post_params
  params.require(:post).permit(:post_category_ids => [])
end

要同时选择多个 Post::Category，我需要将 multiple: 'true' 添加到 View 中的选择中:

<div class="form-group">
  <%= f.label :post_category_ids, :class => 'control-label', :value => 'Category: ' %>
  <%= f.select :post_category_ids, options_from_collection_for_select(all_post_categories, :id, :name), {}, {class: 'selectpicker', :'data-live-search' => 'true', required: 'false', multiple: 'true' } %>
</div>