Rails从一个表单创建多行

# post.rb
class Post < ApplicationRecord
  has_many :comments
  accepts_nested_attributes_for :comments
end

# comment.rb
class Comment < ApplicationRecord
  belongs_to :post
end

# posts_controller.rb
class PostsController < ApplicationController
  def new
    @post = Post.new
    @post.comments.build
  end

  def create
    @post = Post.new(post_params)
    if @post.save
      redirect_to @post
    else
      render 'new'
    end
  end

  private
    def post_params
      params.require(:post).permit(:title, comments_attributes: [:content])
    end
end

# new.html.erb
<%= form_for @post do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title %>

  <%= f.fields_for :comments do |comment_fields| %>
    <%= comment_fields.label :content %>
    <%= comment_fields.text_area :content %>
  <% end %>

  <%= f.submit %>
<% end %>