Activerecord Rails：为nil类创建的未定义方法

我正在创建一个示例项目，但当我试图创建一个新帖子时，出现了一个错误“undefined method create for nil class”

我的代码如下。

user.rb

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  has_one :post, dependent: :destroy
end

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  has_many :posts, dependent: :destroy
end

---

请帮助我并告诉我这两个代码之间的区别是什么？

区别在于添加的帮助器方法允许您构建或创建新的关联对象。与

有多个关联相比，
有一个关联的方法稍有不同

例如，创建新关联对象的方法是
user.create\u post

例如，创建新关联对象的方法是
user.posts.create
谢谢。我使用的是has\u many关联语法。
class PostsController < ApplicationController
  def create
    @user = current_user
    if @user.post.blank?
      @post = @user.post.create(params[:post].permit(:title, :text))
    end
    redirect_to user_root_path
  end
end

<%= form_for([current_user, current_user.build_post]) do |f| %>
  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>
 
  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>
 
  <p>
    <%= f.submit %>
  </p>
<% end %>

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  has_many :posts, dependent: :destroy
end

class Post < ActiveRecord::Base
  belongs_to :user
end

class PostsController < ApplicationController
  def create
    @user = current_user
    if @user.posts.blank?
      @post = @user.posts.create(params[:post].permit(:title, :text))
    end
    redirect_to user_root_path
  end
end

<%= form_for([current_user, current_user.posts.build]) do |f| %>
  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>
 
  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>
 
  <p>
    <%= f.submit %>
  </p>
<% end %>

UserBlog::Application.routes.draw do
  devise_for :users, controllers: { registrations: "registrations" }

  resources :users do
    resources :posts
  end
  # You can have the root of your site routed with "root"
  root 'home#index'
end