rails router: 简单路由与嵌套路由

rails router: 简单路由与嵌套路由

使用rails搭建个人网站，功能杂，一不小心router代码就写的杂乱无章，想要优化router代码就要好好学习rails的router.

## 简单路由

网址url是如何指向到我们想让它去的代码块中，router就是用来干这个的,比如router中这样写：

~~~~ ruby
get '/members/:id', to: 'members#show'
~~~~

`GET /members/17`这个请求会被路由分配到members控制器的show方法中，`{ id: '17' }`会作为参数在show方法中被调用。

如果视图中所有url链接都使用`/members/:id`这种写法来拼出来就太繁琐了，使用路由的name helper方法来生成url链接就方便很多。

~~~~ ruby
get '/members/:id', to: 'members#show', as: 'member'

# 另一种写法

match '/members/:id' => 'members#show', :as => :member, :via => :get
~~~~

上面路由代码中的as指定helper方法名称，默认加_path后缀，`as: 'member'`就会生成name heper 方法`member_path(id)`，在视图中它就会生成`/members/:id`。

~~~~ ruby
#controller
@member = Member.find(17)

#view
<%= link_to 'Member Detail', member_path(@member) %>
#等同于
<%= link_to 'Member Detail', @member %>
#=> /members/17
~~~~

`resources :member`会自动生成以下几条路由，满足基本的CRUD操作:

~~~~ router 
HTTP Verb       Path             Action         Used for
GET            /members           index         display a list of all members
GET            /members/new       new           return an HTML form for creating a new member
POST           /members           create        create a new member
GET            /members/:id       show          display a specific member
GET            /members/:id/edit  edit          return an HTML form for editing a member
PATCH/PUT      /members/:id       update        update a specific member
DELETE         /members/:id       destroy       delete a specific member
~~~~

但我们的需求肯定不止CRUD操作，有新添加的方法后，如何配置路由让它起作用？最简单的方法是使用match.

~~~~ ruby
#定义mx方法，查看用户邮箱的mx记录
match '/members/:id/mx'       => 'members#mx',       :as => :mx_member
~~~~

如果每个控制器都需要添加很多新的方法，都使用match来配置路由，router代码就会显得太乱，不便于日后管理，这时可以resources内部配置新方法，无论添加再多的新方法，对于所属关系就一目了然。

~~~~ ruby
resources :members do
  get 'validate', on: :memebr
  get 'mx', on:member
end

# 会生成下面的路由
#validate_member GET    /members/:id/validate(.:format)                      members#validate
#mx_member GET          /members/:id/mx(.:format)                            members#mx  

# 另一种更简洁的写法

resources :members do
  member do
    get 'validate'
    get 'mx'
  end
end
~~~~


## 嵌套路由
 
### 第一种

url链接前带/admin前缀即/admin/posts，指向Admin::PostsController控制器。

~~~~ ruby
namespace :admin do
  resources :posts
end

#生成的对应name helper

#     admin_posts GET    /admin/posts(.:format)                               admin/posts#index
#                 POST   /admin/posts(.:format)                               admin/posts#create
#  new_admin_post GET    /admin/posts/new(.:format)                           admin/posts#new
# edit_admin_post GET    /admin/posts/:id/edit(.:format)                      admin/posts#edit
#      admin_post GET    /admin/posts/:id(.:format)                           admin/posts#show
#                 PUT    /admin/posts/:id(.:format)                           admin/posts#update
#                 DELETE /admin/posts/:id(.:format)                           admin/posts#destroy
~~~~

### 第二种

url链接中不带有/admin，像简单路由那样，指向 Admin::PostsController控制器。

~~~~ ruby
scope module: 'admin' do
  resources :posts
end

#等价于

resources :posts, module: 'admin'

#生成的对应name helper

#     posts GET    /posts(.:format)                                     admin/posts#index
#           POST   /posts(.:format)                                     admin/posts#create
#  new_post GET    /posts/new(.:format)                                 admin/posts#new
# edit_post GET    /posts/:id/edit(.:format)                            admin/posts#edit
#      post GET    /posts/:id(.:format)                                 admin/posts#show
#           PUT    /posts/:id(.:format)                                 admin/posts#update
#           DELETE /posts/:id(.:format)                                 admin/posts#destroy
~~~~

### 第三种

url链接前带/admin前缀即/admin/posts，但指向PostsController控制器.

~~~~ ruby
scope '/admin' do
  resources :posts
end

#等价于

resources :posts, path: '/admin/posts'

#生成的对应name helper

#     posts GET    /admin/posts(.:format)                               posts#index
#           POST   /admin/posts(.:format)                               posts#create
#  new_post GET    /admin/posts/new(.:format)                           posts#new
# edit_post GET    /admin/posts/:id/edit(.:format)                      posts#edit
#      post GET    /admin/posts/:id(.:format)                           posts#show
#           PUT    /admin/posts/:id(.:format)                           posts#update
#           DELETE /admin/posts/:id(.:format)                           posts#destroy
~~~~

### 第四种

resources的嵌套,会为主子资源生成两套路由，父资源的路由属于简单路由，子资源的路由属于嵌套路由，现在主要研究子资源的路由配置。

~~~~ ruby
#router
resources :magazines do
  resources :ads
end

#生成的对应name helper

#     magazine_ads GET    /magazines/:magazine_id/ads(.:format)                ads#index
#                  POST   /magazines/:magazine_id/ads(.:format)                ads#create
#  new_magazine_ad GET    /magazines/:magazine_id/ads/new(.:format)            ads#new
# edit_magazine_ad GET    /magazines/:magazine_id/ads/:id/edit(.:format)       ads#edit
#      magazine_ad GET    /magazines/:magazine_id/ads/:id(.:format)            ads#show
#                  PUT    /magazines/:magazine_id/ads/:id(.:format)            ads#update
#                  DELETE /magazines/:magazine_id/ads/:id(.:format)            ads#destroy
#        magazines GET    /magazines(.:format)                                 magazines#index
#                  POST   /magazines(.:format)                                 magazines#create
#     new_magazine GET    /magazines/new(.:format)                             magazines#new
#    edit_magazine GET    /magazines/:id/edit(.:format)                        magazines#edit
#         magazine GET    /magazines/:id(.:format)                             magazines#show
#                  PUT    /magazines/:id(.:format)                             magazines#update
#                  DELETE /magazines/:id(.:format)                             magazines#destroy
~~~~

特别说明,在视图中的name helper方法也有相关的约束简洁写法，让name helper方法名称更容易理解、记忆、书写。

~~~~ ruby
#特别说明 - 在view中
#情况一,查看某父资源的子资源明细情况时:

<%= link_to 'Ad details', magazine_ad_path(@magazine, @ad) %>

#等同于

<%= link_to 'Ad details', url_for([@magazine, @ad]) %>
<%= link_to 'Ad details', [@magazine, @ad] %>

###########################################
#情况二，编辑某父资源的子资源信息

<%= link_to 'Ad details', edit_magazine_ad_path(@magazine, @ad) %>

#等同于

<%= link_to 'Edit Ad', [:edit, @magazine, @ad] %>

###########################################
#情况三，查看某父资源的明细情况，其实就是简单路由配置

<%= link_to 'Magazine details', @magazine %>
~~~~


## 父子权力分配

需要理解的是，路由上的嵌套改变不了这样一个事实: **子资源在数据库实体表中的主键id是唯一的**。

创建 、显示子资源时需要父资源来作所属关系，在编辑、删除子资源时是完全可以脱离父资源，尤其是在统一管理子资源时(个人需求，不知道这样合不合理)，显示特别怪异，套用原来的路由配置是需要通过子资源调用出它的父资源才能编辑、更新子资源本身。

为了让子资源脱离父资源的束缚，可以使用**shallow**

~~~~ ruby
resources :magazines do
  resources :ads, shallow: true
end

#等价于
#resources :magazines do
#  resources :ads, only: [:index, :new, :create]
#end
#resources :ads, only: [:show, :edit, :update, :destroy]

#生成的对应name helper

#    magazine_ads GET    /magazines/:magazine_id/ads(.:format)                ads#index
#                 POST   /magazines/:magazine_id/ads(.:format)                ads#create
# new_magazine_ad GET    /magazines/:magazine_id/ads/new(.:format)            ads#new
#         edit_ad GET    /ads/:id/edit(.:format)                              ads#edit
#              ad GET    /ads/:id(.:format)                                   ads#show
#                 PUT    /ads/:id(.:format)                                   ads#update
#                 DELETE /ads/:id(.:format)                                   ads#destroy
#       magazines GET    /magazines(.:format)                                 magazines#index
#                 POST   /magazines(.:format)                                 magazines#create
#    new_magazine GET    /magazines/new(.:format)                             magazines#new
#   edit_magazine GET    /magazines/:id/edit(.:format)                        magazines#edit
#        magazine GET    /magazines/:id(.:format)                             magazines#show
#                 PUT    /magazines/:id(.:format)                             magazines#update
#                 DELETE /magazines/:id(.:format)                             magazines#destroy
                         
#其他写法

resources :magazines, shallow: true do
  resources :ads
end

shallow do
  resources :magazines do
    resources :ads
  end
end
~~~~

使用shadow还可指定url链接前缀、name helper方法名前缀。

+ 指定url链接前缀/edm

~~~~ ruby
scope shallow_path: "edm" do
  resources :magazines do
    resources :ads, shallow: true
  end
end

#生成的对应name helper

#    magazine_ads GET    /magazines/:magazine_id/ads(.:format)                ads#index
#                 POST   /magazines/:magazine_id/ads(.:format)                ads#create
# new_magazine_ad GET    /magazines/:magazine_id/ads/new(.:format)            ads#new
#         edit_ad GET    /edm/ads/:id/edit(.:format)                          ads#edit
#              ad GET    /edm/ads/:id(.:format)                               ads#show
#                 PUT    /edm/ads/:id(.:format)                               ads#update
#                 DELETE /edm/ads/:id(.:format)                               ads#destroy
#       magazines GET    /magazines(.:format)                                 magazines#index
#                 POST   /magazines(.:format)                                 magazines#create
#    new_magazine GET    /magazines/new(.:format)                             magazines#new
#   edit_magazine GET    /magazines/:id/edit(.:format)                        magazines#edit
#        magazine GET    /magazines/:id(.:format)                             magazines#show
#                 PUT    /magazines/:id(.:format)                             magazines#update
#                 DELETE /magazines/:id(.:format)                             magazines#destroy
~~~~

+ 指定name helper路径的前缀

~~~~ ruby
scope shallow_prefix: "edm" do
  resources :magazines do
    resources :ads, shallow: true
  end
end

#生成的对应name helper

#    magazine_ads GET    /magazines/:magazine_id/ads(.:format)                ads#index
#                 POST   /magazines/:magazine_id/ads(.:format)                ads#create
# new_magazine_ad GET    /magazines/:magazine_id/ads/new(.:format)            ads#new
#     edit_edm_ad GET    /ads/:id/edit(.:format)                              ads#edit
#          edm_ad GET    /ads/:id(.:format)                                   ads#show
#                 PUT    /ads/:id(.:format)                                   ads#update
#                 DELETE /ads/:id(.:format)                                   ads#destroy
#       magazines GET    /magazines(.:format)                                 magazines#index
#                 POST   /magazines(.:format)                                 magazines#create
#    new_magazine GET    /magazines/new(.:format)                             magazines#new
#   edit_magazine GET    /magazines/:id/edit(.:format)                        magazines#edit
#        magazine GET    /magazines/:id(.:format)                             magazines#show
#                 PUT    /magazines/:id(.:format)                             magazines#update
#                 DELETE /magazines/:id(.:format)                             magazines#destroy
~~~~

## 参考

[Rails Routing from the Outside In](http://guides.rubyonrails.org/routing.html)