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：

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class Company< ActiveRecord::Base

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

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end

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class User < ActiveRecord::Base

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

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end

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class Address < ActiveRecord::Base

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  belongs_to :addressable, :polymorphic => true

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end

接下来是创建一个Address表来保存地址：

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class CreateAddresses < ActiveRecord::Migration

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  def self.up

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    create_table :addresses do |t|

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      t.string :street_address1, :null => false

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      t.string :street_address2

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      t.string :city, :null => false

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      t.string :region, :null => false

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

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      t.integer :addressable_id, :null => false

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      t.string :addressable_type, :null => false

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      t.timestamps

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    end

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  end

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  def self.down

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    drop_table :addresses

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  end

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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。

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class CompaniesController < ApplicationController

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  def new

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    @company = Company.new

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    @company.address = Address.new

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  end

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  def edit

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

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

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  end

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  def create

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

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

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    if @company.save

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      @company.address.save

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

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      redirect_to(@company)

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    else

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      render :action => 'new'

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    end

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  end

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  def update

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

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

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

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

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      redirect_to(@company)

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    else

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      render :action => 'edit'

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    end

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  end

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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：

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

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    <%= f.error_messages %>

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<dl>

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        <%= f.text_field :name %>

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        <%= f.text_field :telephone %>

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        <%= f.text_field :fax %>

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        <%= f.text_field :website_url %>

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    </dl>

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

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        <%= address_fields.hidden_field :addressable_id %>

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        <%= address_fields.hidden_field :addressable_type %>

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<dl>

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            <%= address_fields.text_field :street_address1 %>

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            <%= address_fields.text_field :street_address2 %>

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            <%= address_fields.text_field :city %>

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            <%= address_fields.text_field :region %>

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            <%= address_fields.text_field :postcode %>

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        </dl>

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    <% end %>

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<% 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。

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

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@address.addressable

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这样就可以访问了。