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一个可能要知道model的数据格式都支持什么 [url=http://hlee.iteye.com/admin/blogs/1015268]可以支持的数据类型[/url] 一个是如果要是创建完了，发现不满意怎么办呢 例如，运行如下：

rails g scaffold task project_id:integer name:string

我的话，第一想到的是git checkout或者git reset 实际上，用如下更合适

rails destroy scaffold task

那么，要是生成了scaffold并且，用了一段了时间了呢 可以先把数据库版本退回来

rake db:rollback STEP=3

当然，通常有数据就不建议rollback了，就要 就要

rails generate migration AddPartNumberToProducts part_number:string

class AddPartNumberToProducts < ActiveRecord::Migration   def self.up     add_column :products, :part_number, :string   end   def self.down     remove_column :products, :part_number   end end

rails generate migration RemovePartNumberFromProducts part_number:string

class RemovePartNumberFromProducts < ActiveRecord::Migration   def self.up     remove_column :products, :part_number   end   def self.down     add_column :products, :part_number, :string   end end

class ExampleMigration < ActiveRecord::Migration   def self.up     create_table :products do |t|       t.references :category     end     #add a foreign key     execute <<-SQL       ALTER TABLE products         ADD CONSTRAINT fk_products_categories         FOREIGN KEY (category_id)         REFERENCES categories(id)     SQL     add_column :users, :home_page_url, :string     rename_column :users, :email, :email_address   end   def self.down     rename_column :users, :email_address, :email     remove_column :users, :home_page_url     execute "ALTER TABLE products DROP FOREIGN KEY fk_products_categories"     drop_table :products   end end

参考： [url]http://asciicasts.com/episodes/216-generators-in-rails-3[/url] [url]http://guides.rubyonrails.org/migrations.html[/url] [url]http://www.viget.com/extend/rails-3-generators-the-old-faithful/[/url]

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