Devise gem已引入但Rails服务器报NoMethodError错误求助

问题情况 #

我是Rails新手，在做Instagram克隆项目时引入devise gem，给导航栏添加了「注册」「登录」「退出」「编辑资料」链接后，服务器抛出NoMethodError错误，提示undefined method 'devise_scope'。虽然对照rails routes配置了链接路径，但问题仍未解决。

导航栏链接代码 #

<li class= "nav-item">
  <%= link_to "Sign Up", new_user_registration_path, class: "nav-link"%>
</li>

<li class= "nav-item">
  <%= link_to "Sign In", new_user_session_path, class: "nav-link"%>
</li>

<li class= "nav-item">
  <%= link_to "Sign Out",  destroy_user_session_path, class: "nav-link"%>
</li>

<li class= "nav-item">
  <%= link_to "Edit Profile", edit_user_registration_path, method: :delete, class: "nav-link"%>
</li>

routes.rb配置 #

Rails.application.routes.draw do
  
  devise_scope :user do
    get '/users', to: 'devise/registrations#new'
    get '/users/password', to: 'devise/passwords#new'
    get '/users/sign_out' => 'devise/sessions#destroy'
  end


  devise_for :users
  get 'posts/new'
  get 'home/about'
  resources :posts
  get "up" => "rails/health#show", as: :rails_health_check
  root "posts#index"
end

错误信息 #

NoMethodError
undefined method `devise_scope' for #<ActionDispatch::Routing::Mapper:0x00007fe912a6e430 @set=#<ActionDispatch::Routing::RouteSet:0x00007fe921d90f00>,
@draw_paths=[#Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/actionview-7.1.3.4/config/routes,
#Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/activestorage-7.1.3.4/config/routes, #Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/actioncable-7.1.3.4/config/routes, #Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/actionmailbox-7.1.3.4/config/routes, #Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/actiontext-7.1.3.4/config/routes, #Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/importmap-rails-2.0.1/config/routes, #Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/turbo-rails-2.0.6/config/routes, #Pathname:/Users/dessy/.rvm/gems/ruby-3.0.0/gems/stimulus-rails-1.3.3/config/routes, #Pathname:/Users/dessy/Desktop/Ruby/PROJECTS/Odin-insta/config/routes, #Pathname:/Users/dessy/Desktop/Ruby/PROJECTS/Odin-insta/config/routes], @scope=#<ActionDispatch::Routing::Mapper::Scope:0x00007fe912a6e3e0 @hash={:path_names=>{:new=>"new", :edit=>"edit"}}, @parent=#<ActionDispatch::Routing::Mapper::Scope:0x00007fe92491c048 @hash=nil, @parent=nil, @scope_level=nil>, @scope_level=nil>, @concerns={}>

问题原因及修正方案 #

1. 解决devise_scope未定义错误 #

devise_scope是Devise提供的路由方法，必须在devise_for :users之后调用——因为devise_for会加载Devise的路由扩展模块，提前调用devise_scope时Rails还未识别该方法，导致报错。同时退出请求需使用DELETE方法，而非GET。

修正后的routes.rb：

Rails.application.routes.draw do
  # 先加载devise_for，再使用devise_scope
  devise_for :users

  devise_scope :user do
    get '/users', to: 'devise/registrations#new'
    get '/users/password', to: 'devise/passwords#new'
    # 修正退出请求的方法为DELETE
    delete '/users/sign_out', to: 'devise/sessions#destroy'
  end

  get 'posts/new'
  get 'home/about'
  resources :posts
  get "up" => "rails/health#show", as: :rails_health_check
  root "posts#index"
end

2. 修正导航栏链接的请求方法错误 #

• 退出链接：Devise默认的退出路由是DELETE请求，原代码未指定method: :delete会导致路由匹配失败，需添加该参数。
• 编辑资料链接：原代码错误添加了method: :delete，编辑页面是GET请求，需移除该参数。

修正后的导航栏代码：

<li class="nav-item">
  <%= link_to "注册", new_user_registration_path, class: "nav-link"%>
</li>

<li class="nav-item">
  <%= link_to "登录", new_user_session_path, class: "nav-link"%>
</li>

<li class="nav-item">
  <%= link_to "退出", destroy_user_session_path, method: :delete, class: "nav-link"%>
</li>

<li class="nav-item">
  <%= link_to "编辑资料", edit_user_registration_path, class: "nav-link"%>
</li>

验证方法 #

运行rails routes命令，查看生成的路由列表，确认destroy_user_session对应的请求方法是DELETE，edit_user_registration对应的是GET。

内容的提问来源于stack exchange，提问作者Dessy