Ruby on rails newbie here。试图创建一个入门博客应用程序,并在我的模型之间存在多对多的关联。
我有两个模型 - 帖子,类别,彼此之间有多对多关联。
我的问题:当我创建新帖子时,帖子会被保存,但是类别后关联不会保存在categories_posts表中。
我的代码如下。
感谢您对此的投入。
post.rb
class Post < ActiveRecord::Base
validates_presence_of :title, :body, :publish_date
belongs_to :user
has_and_belongs_to_many :categories
end
category.rb
class Category < ActiveRecord::Base
validates_presence_of :name
has_and_belongs_to_many :posts
end
categories_posts.rb
class CategoriesPosts < ActiveRecord::Base
end
迁移 - create_posts.rb
class CreatePosts < ActiveRecord::Migration
def change
create_table :posts do |t|
t.string :title
t.text :body
t.date :publish_date
t.integer :user_id
t.timestamps
end
end
end
迁移 - create_categories.rb
class CreateCategories < ActiveRecord::Migration
def change
create_table :categories do |t|
t.string :name
t.timestamps
end
end
end
迁移 - create_categories_posts.rb
class CreateCategoriesPosts < ActiveRecord::Migration
def change
create_table :categories_posts do |t|
t.integer :category_id
t.integer :post_id
t.timestamps
end
end
end
后置控制器 - 创建和新方法
#GET /posts/new
def new
@post = Post.new
end
def create
@post = Post.new(post_params)
#User id is not a form field and hence is not assigned in the view. It is assigned when control is transferred back here after Save is pressed
@post.user_id = current_user.id
respond_to do |format|
if @post.save
format.html { redirect_to @post, notice: 'Post was successfully created.' }
format.json { render action: 'show', status: :created, location: @post }
else
format.html { render action: 'new' }
format.json { render json: @post.errors, status: :unprocessable_entity }
end
end
end
发布视图(用于创建新帖子):
<%= simple_form_for @post, :html => { :class => 'form-horizontal' } do |f| %>
<%= f.input :title %>
<%= f.input :body %>
<%= f.input :publish_date %>
<%= f.association :categories, :as => :check_boxes %>
<div class="form-actions">
<%= f.button :submit, :class => 'btn-primary' %>
<%= link_to t('.cancel', :default => t("helpers.links.cancel")),
posts_path, :class => 'btn' %>
</div>
<% end %>
谢谢, 麦克
答案 0 :(得分:14)
使用has_and_belongs_to_many
关联时,您需要在联接表上使用唯一索引。您的迁移应如下所示:
class CreateCategoriesPosts < ActiveRecord::Migration
def change
create_table :categories_posts do |t|
t.integer :category_id
t.integer :post_id
t.timestamps
end
add_index :categories_posts, [:category_id, :post_id]
end
end
您还可以摆脱CategoriesPost模型,只有在您想要实现:has_many, :through
关联时才需要。这应该回答你的问题。
而且要彻底,如果您想使用与{Version}}模型的:has_many, :through
关联,您可以这样实现:
class Post < ActiveRecord::Base
has_many :categoriesposts
has_many :categories, :through => :categoriesposts
end
class Category < ActiveRecord::Base
has_many :categoriesposts
has_many :posts, :through => :categoriesposts
end
class CategoriesPost < ActiveRecord::Base
belongs_to :post
belongs_to :category
end
如果需要,实现此方法可以为categorypost模型添加更多属性。
答案 1 :(得分:0)
在第一个答案之后,您需要将关联放在您的连接模型(CategoriesPosts)中,如下所示:
Class CategoriesPosts < ActiveRecord::Base
belongs_to :category
belongs_to :post
End