Question

我在我的Rails 5.1.3应用程序中将Tag设置为多态模型。我正在尝试设置collection_select，以便我可以从下拉菜单中选择标记。

表单创建新标签，关联效果很好，但是，我无法将标签名称传递到表单中，因此我的标签将name保存为空字符串。

_form.html.erb

<%= form_for [taggable, Tag.new] do |f| %>
  <%= f.collection_select :taggable_id, Tag.order(:name), :id, :name %>
  <%= f.submit %>
<% end %>

tags_controller.rb

class TagsController < ApplicationController
before_action :authenticate_user!

def create
  @tag = @taggable.tags.new(tag_params)
  @tag.user_id = current_user.id

  if @tag.save  
    redirect_to book_path(@taggable.book_id), notice: "Tag saved"
  else
    redirect_to root_path, notice: "Sorry, something went wrong"
  end
end

private

  def tag_params
    params.require(:tag).permit(:name)
  end

端

Tag params：

=> <ActionController::Parameters {"utf8"=>"✓", "authenticity_token"=>"z2PLrvETqtq742zmr3pghEYYqoGoLv05gLP3OXopLM+blWWw+HmR4AMMDB+5ET3E5YLXeyhMCFMHfdxJNHlkZA==", "tag"=><ActionController::Parameters {"taggable_id"=>"1"} permitted: false>, "commit"=>"Create Tag", "controller"=>"books/tags", "action"=>"create", "book_id"=>"26"} permitted: false>

编辑：添加模型和字段

book.rb

class Book < ApplicationRecord
  has_many :tags, as: :taggable
end

tag.rb

class Tag < ApplicationRecord
 belongs_to :taggable, polymorphic: true
end

标签表

create_table "tags", force: :cascade do |t|
  t.string "taggable_type"
  t.integer "taggable_id"
  t.integer "user_id"
  t.text "name"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
end

Answer 1

问题是你正在接近这个问题。

标记只能属于单一资源的标记系统作为分类法几乎毫无价值。相反，您需要与连接表进行多对多关联：

# app/models/tag.rb
class Tag < ApplicationRecord
  has_many :taggings
  has_many :taggables, through: :taggings
end

# This join model represents a tag attached to a resource
# app/models/tagging.rb
class Tagging < ApplicationRecord
  belongs_to :tag
  belongs_to :taggable, polymorphic: true
end

# We extract the taggable feature to a concern so that we don't have to repeat it.
# app/models/concerns/taggable.rb
module Taggable
  extends ActiveSupport::Concern

  included do
    has_many :taggings, as: :taggable
    has_many :tags, through: :taggings
  end
end

# app/models/book.rb
class Book < ApplicationRecord
  include Taggable
end

# just an example
class Film < ApplicationRecord
  include Taggable
end

这使用tags作为规范化表，而不是在表中反复复制名称。这使您可以获得具有特定标签的书籍，而无需使用比使用索引列上的连接慢得多的文本搜索。

要在Taggable上设置多个标记，您可以使用ActiveRecord为has_many关联创建的tag_ids= setter：

<%= form_for(@book) do |f| %>
  <%= f.text_input :title %>
  <%= f.collection_select :tag_ids, Tag.order(:name), :id, :name, multiple: true %>
  <%= f.submit %>
<% end %>

这是作为可标记（父）资源的正常创建/更新操作的一部分完成的。可以一次创建单个标记（创建连接记录），但不是很有用。

另一方面，

POST /books/:book_id/tags将用于创建单个标记并设置关联：

<%= form_for([@taggable, @tag]) do |f| %>
  <%= f.label :name do %>
    <%= f.text_input :name %>
  <% end %>
  <%= f.submit %>
<% end %>

class TagsController
  before_action :set_taggable

  # POST /books/:book_id/tags
  def create
    @tag = @taggable.tag.new(tag_params)

    if @tag.save
      redirect_to @taggable, success: "New tag created."
    else
      render :new
    end
  end

  def set_taggable
    @taggable = Book.find(params[:book_id])
  end

  def tag_params
    params.require(:tag).permit(:name)
  end
end

然而，通过大量使用Ajax，您可以让用户通过发送POST /tags请求来“内联”创建标记，从而提供更好的用户体验。

collection_select用于多态模型

1 个答案: