为has_many关系创建方法？

class Blog< ApplicationRecord
  has_many :posts
end

class Post< ApplicationRecord
  belongs_to :blog
end

class BlogsController< ApplicationController
  def show
    @blog = Blog.find(params[:id])
    @posts = @blog.posts
  end
end

class PostsController< ApplicationController
  def create
    @blog = Blog.find(params[:blog_id])
    @post = @blog.posts.build(post_params)
    if @post.save
      redirect_to blog_path(@blog)
    else
      render 'new'
    end
  end

  private

  def post_params
    params.require(:post).permit(:title, :content)
  end
end

<h1><%= @blog.title %></h1>
<p><%= @blog.content %></p>

<h2>Posts</h2>
<ul>
  <% @posts.each do |post| %>
    <li>
      <h3><%= post.title %></h3>
      <p><%= post.content %></p>
    </li>
  <% end %>
</ul>