rails restful 详细介绍

REST, Resources, and Rails

Before REST came I (and pretty much everyone else) never really knew where to
put stuff.
—Jonas Nicklas on the Ruby on Rails mailing list

Routing and CRUD
当你在routes.rb里这么写的时候:
map.resources :auctions
你就已经创造了4个具名路由,实际上允许你访问7个action(index, create, show,
update, destroy, new, edit)。

/auctions GET

/auctions POST

HTTP方法不同,尽管url相同,仍然还是两个不同的东西。来看一个RESTFul的路由表,显示了helpers,paths,以及controller action的关系:
Helper
client_url(@client) - /clients/1 (show) ; /clients/1 (update); /clients/1 (destroy)
clients_url - /clients (index) ; /clients (create)
edit_client_url(@client) - /clients/1/edit (edit)
new_client_url - /clients/new (new)


当你生成一个URL的时候,你需要知道如何指定request方法,以防止你在GET /cients和POST /cients的时候触发了同一个action。看下面的一些规则:

默认的request 方法是GET
在form_for和form_tag方法被调用的时候,POST会被自动调用。
你也能通过具名路由专门指定你需要的(几乎最多的是PUT 和 DELETE)。
例子:
<%= link_to “Delete this auction”,:url => auction(@auction),:method => :delete %>
当调用update action的时候,需要指定PUT方法。
<% form_for “auction”, :url => auction(@auction),:html => { :method => :put } do |f| %>


The PUT and DELETE Cheat
浏 览器通常不会支持GET, POST以外的HTTP方法,为了发送PUT,DELETE请求,Rails做了一些小技巧。 PUT, DELETE请求,在Rest in Rails的上下文中,实际上是带有一个隐藏域“_method”方法的POST, 这个隐藏域来设置是‘put’还是‘delete’。

Singular and Plural RESTful Routes
一些Restful路由是单数的,一些是复数的,规则如下:
show,new, edit和destroy的路由是单数的,因为它们只为单独的资源工作。
其余action的路由都是复数,因为它们要处理相关资源的集合。
单数Restful路由需要一个参数,因为它需要指定你要操作资源的id:
item_url(@item) # show, update, or destroy, depending on HTTP verb
也可以用Hash的形式:
item_url(:id => @item)
你没必要一定要调用@item的id方法,Rails会帮你完成的。

The Special Pairs: new/create and edit/update
new / edit : 是用来得到form表单显示的。
create/update:是用来处理form提交的数据的。

new action,可以理解是得到一个单独的新的资源。但是HTTP动词GET,已经用在了show action上,所以new就必须有一个属于自己的名字。 这就是为什么我们需要这么使用:
<%= link_to “Create a new item”, new_item_path %>

edit action, 可以理解为给你一个不是正式的资源,是具有修改性质的的show资源,所以,这么用:
edit_item_url(@item)

Singular Resource Routes
map.resources也有map.resource这样的单数形式。
它一般被用在你应用上下文里仅出现一次的资源。看例子:
假如有个地址簿的应用,可能给每一个登陆用户一个地址簿,所以你可以写:
map.resource :address_book
你就会得到:
GET/PUT address_book_url,
GET edit_address_book_url,
PUT update_address_book_url.

注意以上这个例子所有的具名路由都是单数的。它是假定这个通信录在对于一个用户是唯一的。这里没有任何魔术,你必须登陆并且从数据库查找属于那个用户的address book, 路由只是给你提供个方便罢了。


Nested Resources
拿书里的竞标例子来说,每一次投标(bid)都关联着同一个auction。这意味着:
auction has_many bids
就像这样的:/auctions/3/bids/5
为什么不只是留下bids/5而跳过前面的auctions呢?
你可以从url上看出资源的信息。
这种url可以让你使用params[:auctions_id]来访问auction的id。

想创建嵌套资源,只需要在routes.rb里这么写:
map.resources :auctions do |auction|
auction.resources :bids
end

请注意里面的资源,是auction. 而不是map.
你可以使用,auction_bids_url, new_auction_bid_url等等。
<%= link_to “See all bids”, auction_bids_path(@auction) %>
这样你可以得到:/auctions/3/bids
你能通过params[:auction_id]找到@auction的id。

对于单独的bid资源(show,edit,destroy)你需要使用最少两个参数:
<%= link_to “Delete this bid”,
auction_bid_path(@auction, @bid), :method => :delete %>

你也可以使用hash的形式,但是大部分人不喜欢长代码:
auction_bid_path(:auction => @auction, :bid => @bid)


Setting :path_prefix Explicitly
设置前缀。
map.resources :auctions
map.resources :bids, :path_prefix => “auctions/:auction_id”

这个前缀和上面的嵌套资源实现的结果一样。但是和嵌套资源比这种方式更常用。

Setting :name_prefix Explicitly
可以控制你路由生成helper的方式。比如:
bid_path(@auction, @bid) 得到 /auctions/2/bids/5
bid_path(@bid) 得到 /bids/5

想实现这个功能,你只需要重写嵌套资源的name_prefix。
map.resources :auctions do |auction|
auction.resources :bids, :name_prefix => nil
end

你可能也想要这种helper方法:
bid_path(@auction, @bid) # /auctions/1/bids/1
bid_path(@person, @bid) # /people/1/bids/1

map.resources :auctions do |auction|
auction.resources :bids, :name_prefix => nil
end
map.resource :people do |people|
people.resources :bids, :name_prefix => nil # are you sure?
end


Specifying RESTful Controllers Explicitly
资源和controller的对应,是根据命名约定自动映射的。比如:
map.resources :auctions do |auction|
auction.resources :bids
end
对应的是AuctionsController和BidsController.你也可以自己指定controller:
map.resources :my_auctions, :controller => :auctions do |auction|
auction.resources :my_bids, :controller => :bids
end

All Together Now
现在我们知道了:name_prefix, :path_prefix, :controller三个选项。我们把它们一起来使用:

map.resources :auctions do |auction|
auction.resources :bids, :name_prefix => nil,
:controller => :auction_bids
end
map.resource :people do |people|
people.resources :bids, :name_prefix => nil,
:controller => :person_bids
end

AuctionBidsController和PersonBidsController会继承同一个父类BidsController。

class BidsController < ApplicationController
before_filter :load_parent
before_filter :load_bid

protected
def load_parent
# overriden in subclasses
end

def load_bid
@bids = @parent.bids
end
end

class AuctionBidsController < BidsController
protected
def load_parent
@parent = @auction = Auction.find(params[:auction_id])
end
end

class PersonBidsController < BidsController
protected
def load_parent
@parent = @person = Person.find(params[:person_id])
end
end


Deep Nesting?

map.resources :auctions do |auctions|
auctions.resources :bids do |bids|
bids.resources :comments
end
end
三层嵌套,这样可读性差。我们一般可以修改为:
map.resources :auctions do |auctions|
auctions.resources :bids
end
map.resources :bids do |bids|
bids.resources :comments
end
map.resources :comments

这样helper方法也容易去用:
auctions_path # /auctions
auctions_path(1) # /auctions/1
auction_bids_path(1) # /auctions/1/bids
bid_path(2) # /bids/2
bid_comments_path(3) # /bids/3/comments
comment_path(4) # /comments/4

RESTful Route Customizations
/auctions/3/bids/5/retract

map.resources :auctions do |a|
a.resources :bids, :member => { :retract => :get }
end

<%= link_to “Retract”, retract_bid_path(auction, bid) %>
也有:collection选项。

Formatted Named Routes
带格式的具名路由。

<%= link_to “XML version of this auction”,formatted_auction_path(@auction, “xml”) %>

会生成下列html:
XML version of this auction


Reflecting on Rails Routing

You are in a maze of twisty little passages, all alike.
—Adventure (late 70s-era computer game)

Examining Routes in the Application Console
你可以在控制台检测你的路由系统。

Dumping Routes

$ ruby script/console
Loading development environment.
>> rs = ActionController::Routing::Routes
>> puts rs.routes

你可以看到全部定义好的路由:
GET /bids/ {:controller=>”bids”, :action=>”index”}
GET /bids.:format/ {:controller=>”bids”, :action=>”index”}
… …

Recognition and Generation in the Console
$ ./script/console
Loading development environment.
>> irb ActionController::Routing::Routes
>>
irb这个命名,会在console里面生成一个默认的self对象,self是指ActionController::Routing::Routes这个的对象。
你可以尝试以下命令:

>> generate(:controller => “bids”, :auction_id => 3, :action =>
“create”)
=> “/auctions/3/bids”

>> generate(:controller => “items”, :action => “item_year”, :year =>
1939)
=> “/item_year/1939”
>> generate(:controller => “items”, :action => “item_year”, :year =>
19393)
=> “/items/item_year?year=19393”
这个例子里year参数是4个数字,但是如果输入的不符合规范,则生成第二种url。


>> recognize_path(“/”)
=> {:controller=>”auctions”, :action=>”index”}

>> recognize_path(“/auctions”, :method => :get)
=> {:controller=>”auctions”, :action=>”index”}

>> recognize_path(“/auctions”, :method => :post)
=> {:controller=>”auctions”, :action=>”create”}

>> recognize_path(“/auctions/3/bids”, :method => :post)
=> {:controller=>”bids”, :action=>”create”, :auction_id=>”3”}

>> recognize_path(“/users/3/bids/1/retract”, :method => :get)
=> {:controller=>”bids”, :user_id=>”3”, :action=>”retract”, :id=>”1”}

>>exit
>>#, @signal_status=:IN_EVAL, @scanner=#>


Named Routes in the Console
你也可以在控制台里执行命名路由。如下:
>> include ActionController::UrlWriter
=> Object
>> default_url_options[:host] = “example.com”
=> “example.com”
>>
>> auction_url(1)
=> “http://example.com/auctions/1”
>> formatted_auction_url(1,”xml”)
=> “http://example.com/auctions/1.xml”
>> formatted_auctions_url(“xml”)
=> “http://example.com/auctions.xml”

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