Polymorphic form--多态表单

一个ruby on rails项目，用户和公司的模型都有地址。

我要创建一个地址表，包含用户和公司表的引用，比直接做下去要好一点，这回让我的数据库设计保持干净。

我的第一印象是，这似乎很难实现，外面所有的讨论及教程都只说明了在model如何设置，但是并没有说明在controller和view如何使用它。我好一顿放狗，也没有得到太多的帮助。

令我感到惊喜是其实在rails设置并使用多态表单是很简单的。

首先依然是先设置model结构：

01	class Company< ActiveRecord::Base

02	has_one :address, :as =>; :addressable, :dependent => :destroy

03

end

04

05	class User < ActiveRecord::Base

06	has_one :address, :as => :addressable, :dependent => :destroy

07

end

08

09	class Address < ActiveRecord::Base

10	belongs_to :addressable, :polymorphic => true

11

end

接下来是创建一个Address表来保存地址：

01	class CreateAddresses < ActiveRecord::Migration

02	def self.up

03	create_table :addresses do |t|

04	t.string :street_address1, :null => false

05	t.string :street_address2

06	t.string :city, :null => false

07	t.string :region, :null => false

08	t.string :postcode, :null => false, :limit => 55

09	t.integer :addressable_id, :null => false

10	t.string :addressable_type, :null => false

11

12	t.timestamps

13

end

14

end

15

16	def self.down

17	drop_table :addresses

18

end

19

end

接下来是controller，你只需要修改controller中的"new","create","edit","update"四个action，好让需要的时候可以访问和修改address。

01	class CompaniesController < ApplicationController

02

03

def new

04	@company = Company.new

05	@company.address = Address.new

06

end

07

08

def edit

09	@company = Company.find(params[:id])

10	@company.address = Address.new unless @company.address != nil

11

end

12

13	def create

14	@company = Company.new(params[:company])

15	@company.address = Address.new(params[:address])

16

17	if @company.save

18	@company.address.save

19	flash[:notice] = 'Company was successfully created.'

20	redirect_to(@company)

21

else

22	render :action => 'new'

23

end

24

end

25

26	def update

27	@company = Company.find(params[:id])

28

29	if @company.update_attributes(params[:company])

30	@company.address.update_attributes(params[:address])

31	flash[:notice] = 'Company was successfully updated.'

32	redirect_to(@company)

33

else

34	render :action => 'edit'

35

end

36

end

37

end

最后一件事是让address在表单中可以正常工作，我们这里使用field_for方法：

01	<% form_for(@company) do |f| %>

02	<%= f.error_messages %>

03

<dl>

04	<%= f.text_field :name %>

05	<%= f.text_field :telephone %>

06	<%= f.text_field :fax %>

07	<%= f.text_field :website_url %>

08

</dl>

09

10	<% fields_for(@company.address) do |address_fields| %>

11	<%= address_fields.hidden_field :addressable_id %>

12	<%= address_fields.hidden_field :addressable_type %>

13

<dl>

14	<%= address_fields.text_field :street_address1 %>

15	<%= address_fields.text_field :street_address2 %>

16	<%= address_fields.text_field :city %>

17	<%= address_fields.text_field :region %>

18	<%= address_fields.text_field :postcode %>

19

</dl>

20

21

<% end %>

22

<% end %>

到这就应该可以正常工作了。

有人要问了，如果我去的了address对象，能否反向取得Company或者User对象呢？答案当然是肯定的。

1	@address = Address.find(params[:id])

2	@address.addressable

3

这样就可以访问了。