在Rails中创建多态关联的表单

Question

我有几个类,每个都有评论:

class Movie < ActiveRecord::Base
    has_many :comments, :as => :commentable
end

class Actor < ActiveRecord::Base
    has_many :comments, :as => :commentable
end

class Comment < ActiveRecord::Base
    belongs_to :commentable, :polymorphic => true
end

如何为新电影评论创建表单？我补充道

resources :movies do
    resources :comments
end

到我的routes.rb,并尝试了new_movie_comment_path(@movie),但这给了我一个包含commentable_id和commentable_type的表单[我希望自动填充,而不是由用户直接输入].我也试过自己创建表单:

form_for [@movie, Comment.new] do |f|
    f.text_field :text
    f.submit
end

(其中"text"是Comment表中的一个字段)但这也不起作用.

我真的不确定如何将评论与电影联系起来.例如,

c = Comment.create(:text => "This is a comment.", :commentable_id => 1, :commentable_type => "movie") 

似乎没有创建与ID为1的电影关联的注释.(Movie.find(1).comments返回一个空数组.)

Answer 1

由于您已在模型中创建了多态关联,因此您无需再在视图中担心这种关联.您只需要在Comments控制器中执行此操作.

@movie = Movie.find(id) # Find the movie with which you want to associate the comment
@comment = @movie.comments.create(:text => "This is a comment") # you can also use build
# instead of create like @comment = @movie.comments.create(:text => "This is a comment")
# and then @comment.save
# The above line will build your new comment through the movie which you will be having in
# @movie.
# Also this line will automatically save fill the commentable_id as the id of movie and 
# the commentable_type as Movie.