Ruby On Rails Active Admin has_many 下拉列表添加新对象答案

【问题标题】：Ruby On Rails Active Admin has_many dropdown to add new objectRuby On Rails Active Admin has_many 下拉列表添加新对象
【发布时间】：2017-06-03 18:07:44
【问题描述】：

我有一个模型与另一个模型具有自引用 has_many 关系。所以我有模型Product，每个产品可以有另一个产品。

class Project < ActiveRecord::Base
  has_many :project_connections
  has_many :related_projects, through: :project_connections,
                              dependent: :destroy
  accepts_nested_attributes_for :project_connections,
                                :related_projects, allow_destroy: true

  ...
end

还有我的ProjectConnection 模特：

class ProjectConnection < ActiveRecord::Base
  belongs_to :project
  belongs_to :related_project, class_name: Project

  accepts_nested_attributes_for :project
  accepts_nested_attributes_for :related_project

  ...
end

在 Active Admin 中，我想在创建/编辑项目视图中删除或添加相关项目。在admin/project.rb

form do |f|
    inputs 'Продолжение проекта' do
      f.has_many :related_projects, heading: 'Добавьте проект', allow_destroy: true, new_record: true  do |i|
        i.input :id, as: :select, collection: Project.all, include_blank: false
      end
    end
end

http://localhost:3000/admin/projects/1/edit

添加新的related_project 并按更新项目后，没有任何改变。那么我应该怎么做才能解决这个问题呢？谢谢。

【问题讨论】：

标签： ruby-on-rails ruby activeadmin

【解决方案1】：

一个可能的解决方案是在项目中使用一个抽象字段 connected_project_ids 和一个 before_save 过滤器来持久化更改，并在加载后填充该字段以初始化表单

before_save   :connect_projects
after_find    :set_connected_project_ids
attr_accessor :connected_project_ids

def set_connected_project_ids
  self.connected_project_ids = connected_projects.pluck(:related_project_id)
end

def connect_projects
  connected_ids = connected_projects.pluck(:related_project_id)

  #projects that are in connected_project_ids, but not yet associated
  projects_to_connect = connected_project_ids - connected_ids
  projects_to_connect.each do |cp_id|
    connected_projects.create(related_project_id: cp_id) 
  end

  #projects that are associated, but not in connected_project_ids
  projects_to_disconnect = connected_ids - connected_project_ids
  projects_to_disconnect.each do |cp_id|
    connected_projects.where(related_project_id: cp_id).destroy_all
  connected_ids
end

这将允许您通过在 connected_project_ids 字段中提交现在应该与之关联的项目 ID 数组来添加和删除关联的项目。

【讨论】：

【解决方案2】：

所以，我自己解决了问题。由于 ProjectConnection 存储项目 {id、project_id、related_project_id} 之间的连接，因此使用 projects.project_connections 而不是 projects.related_projects 进行操作是正确的。首先，我在admin/project.rb 中为projects.project_connections 声明了一个参数结构：

project_connections_attributes: [
  :id,
  :project_id,
  :related_project_id,
  :_destroy
]

然后代替

inputs 'Продолжение проекта' do
  f.has_many :related_projects, heading: 'Добавьте проект', allow_destroy: true, new_record: true  do |i|
    i.input :id, as: :select, collection: Project.all, include_blank: false
  end
end

我写的

inputs 'Продолжение проекта' do
  f.has_many :project_connections, heading: 'Добавьте проект', allow_destroy: true, new_record: true  do |i|
    i.input :related_project_id, as: :select, collection: Project.all, include_blank: false
    i.input :project_id, :input_html => { :value => f.object.id }, as: :hidden
  end
end

效果很好）

【讨论】：