@@ -11,15 +11,15 @@ <div class="halftitlepage"> <h1 class="no-toc">Ruby on Rails 2.1</h1> - <h2 class="no-toc">What's New</h2> - <h3 class="no-toc">Second Edition</h3> + <h2 class="no-toc">新特性介绍</h2> + <h3 class="no-toc">第二版 (中文版)</h3> </div> <div class="titlepage"> <h1 class="no-toc">Ruby on Rails 2.1</h1> - <h2 class="no-toc">What's New</h2> - <h3 class="no-toc">Second Edition</h3> + <h2 class="no-toc">新特性介绍</h2> + <h3 class="no-toc">第二版 (中文版)</h3> <p class="no-toc">Carlos Brando<br/>Marcos Tapajós</p> <!-- also, the publisher's name would typically be printed here --> layout/pdf_template.html @@ -42,8 +42,8 @@ class Prince path << ' --silent - -o -' # Show the command used... - puts "\n\nPRINCE XML PDF COMMAND" - puts path + #logger.info "\n\nPRINCE XML PDF COMMAND" + #logger.info path #logger.info '' # Actually call the prince command, and pass the entire data stream back. script/prince.rb @@ -1,10 +1,11 @@ -#Introduction +#概述(Introduction) -Around July of 2004 David Heinemeier Hansson publicly released the Ruby on Rails framework. The framework had been extracted from a web application called he was working on called Basecamp. More than three years later, on the December 7th 2007, Ruby on Rails version 2.0 was released with numerous important changes. +2004年7月，David Heinemeier Hansson从其项目 Basecamp中抽取并发布了 Ruby On Rails框架。三年后的2007年12月7日，具有划时代意义的 Ruby On Rails 2.0版本发布了，其中包含了一系列的新内容。 -Six months have passed since then, and during this time more than **1400 developers** from all around the world have contributed **1600 patches** to the framework. Today, June 1st 2008, version 2.1 of the Ruby on Rails framework was released. +接下来的六个月，全世界**1400**多名开发者为 Rails贡献了**1600**多个patch，今天,2008年6月1日,Ruby On Rails +2.1发布了。 -Major new features according to David Heinemeier Hansson: +本次发布包含但不限于如下功能点: * Timezones * Dirty tracking @@ -13,42 +14,69 @@ Major new features according to David Heinemeier Hansson: * UTC-based migrations * Better caching -As always, to update or install the new version: +和以往一样，更新Rails很简单： gem install rails -##Acknowledgment +##致谢 -To Marcos Tapajós, co-author of this book. If it wasn't for him, you probably you wouldn't be reading this right now. +感谢Marcos Tapajós,如果没有他，我们到现在肯定看不到这本书；感谢Daniel Lopes给本书制作了漂亮的封面； -To Daniel Lopes who made the beautiful cover for this edition. +还有Ruby on Rails Brazilian中那些直接或者间接给本书提供帮助的朋友们，您们的评论和建议都弥足珍 贵，正像我以往说的一样，Rails中最精华的是其充满激情、创造力和分享精神的社区； -To all of the Ruby on Rails Brazilian community that helped directly or indirectly with this book, commenting on blog posts and giving suggestions. It's like I always say, the best of Rails is its community! Keep creating, inventing, and specially sharing. +还有chinaonrails.com社区中的朋友们，正是大家的辛勤工作，才使得我们能这么短的时间内即可完成 +翻译，谢谢你们。 -## Translators +##中文译者 -This book was proudly translated to english by these Brazilian guys: +本书正是由China on Rails社区中一些朋友翻译成中文的,我们是： -**Pedro Pimentel** - [http://www.pedropimentel.com](http://www.pedropimentel.com) +**IceskYsl** +[http://iceskysl.1sters.com/](http://iceskysl.1sters.com/) -Chapters 3-8 and 10-13 +第1章(Introduction)，第9章(Rake Tasks, Plugins and Scripts) +第11章(Ruby 1.9)，第14章(Additional Information). -**Rafael Barbosa** - [http://www.act-as-newbie.com](http://www.act-as-newbie.com/) +**jesse.cai** +[http://www.caiwangqin.com/](http://www.caiwangqin.com) -Introduction and chapter 1 +第5章(ActionPack)，第12章(Debug) -**Ricardo S Yasuda** - [http://blog.shadowmaru.org](http://blog.shadowmaru.org/) +**suave.su** +[http://chinaonrails.com/u/suave](http://chinaonrails.com/u/suave) +第1章(Introduction) -Chapter 14 +**dongbin** +[http://dongbin.org/](http://dongbin.org/) -**Caike Souza** - [http://tech-death.blogspot.com](http://tech-death.blogspot.com/) +第3章(ActiveSupport) -Chapter 2 +**海阳** +[http://rubyjin.cn/](http://rubyjin.cn/) -**Abraão Coelho** - [http://abrcoelho.net](http://abrcoelho.net/) +第6章(ActionController) -Chapter 9 +**404** +[http://chinaonrails.com/u/404](http://chinaonrails.com/u/404) -**Bruno Miranda** - [http://brunomiranda.com](http://brunomiranda.com) +第8章(Railties) -Reviser \ No newline at end of file +**ashchan** +[http://blog.ashchan.com/](http://blog.ashchan.com/) + +第4章(ActiveResource),第10章(Prototype and script.aculo.us) + +**cash.zhao** +[http://www.cashplk.com/](http://www.cashplk.com/) + +第7章(ActionView),第13章(Bugs and Fixes) + +**snow zhang** +[http://blog.snowonrails.com](http://blog.snowonrails.com) + +第2章(ActiveRecord) + +**Libin Pan** +[http://blog.libinpan.com](http://blog.libinpan.com) + +Markdown Editor \ No newline at end of file text/0/0_Title.markdown @@ -1,4 +1,3 @@ # ActiveRecord - -ActiveRecord is an object-relational mapping layer responsible for the interoperability among application -and database and also responsible for data abstraction. (wikipedia) \ No newline at end of file + +ActiveRecord是一个对象-关系映射层，主要负责应用层和数据层之间的互操作性(解耦)以及数据抽象。(wikipedia) \ No newline at end of file text/01_ActiveRecord/00.markdown @@ -1,15 +1,13 @@ -## The **sum** method +## **sum**方法 -### Expressions in the **sum** method - -Now we can use expressions in **ActiveRecord** methods that deal with calculation, like **sum**, for example: +### **sum**方法中的表达式 - Person.sum("2 * age") +现在我们可以在**ActiveRecord**方法当中使用表达式来处理诸如**sum**等各种计算，如： -### Change in the default return value of the sum method + Person.sum("2 * age") -On previous versions, when we used **ActiveRecord**'s **sum** method to calculate the addition of all rows in a table and no row matched the conditions expressed during the method invocation, then the default return value would be **nil**. +### **sum**方法默认返回值的改变 -In Rails 2.1 the default return value (that is when no row is found) is 0. See the example: +在之前的版本中，当我们使用**ActiveReocrd**的**sum**方法来计算表中所有记录的和的时候，如果没有跟所需条件匹配的记录的时候，则默认的返回值是**nil** 。在 Rails2.1 中，默认返回值(当没有匹配的记录的时候)是0。如: Account.sum(:balance, :conditions => '1 = 2') #=> 0 text/01_ActiveRecord/01_sum.markdown @@ -1,8 +1,8 @@ ## Has\_one -### Support for the option through +### 支持 through 选项 -The **has\_one** method now has the option **through**. It works just like **has_many :through**, but it represents the association to a single **ActiveRecord** object. +**has\_one**方法现在支持**through**选项。他的用法与**has_many:through**相同，不过代表的是和单一一个**ActiveRecord**对象的关联. class Magazine < ActiveRecord::Base has_many :subscriptions @@ -19,19 +19,17 @@ The **has\_one** method now has the option **through**. It works just like **has :conditions => ['subscriptions.active = ?', true] end -### Has\_one with :source\_type - -The **has\_one :through** method, just mentioned above, can also take **:source\_type**. I will try to explain this through some examples. Let's start with these two classes: +### Has\_one :source\_type 选项 + +上边提到的**has\_one :through**方法还能接收一个**:source\_type**选项，我会试着通过一些例子来解释。我们先来看看这个类： class Client < ActiveRecord::Base has_many :contact_cards has_many :contacts, :through => :contact_cards end - -What we are looking at here is a **Client** class which **has_many** kinds of contacts, since the **ContactCard** class has a polymorphic relationship. -Next step in our example, let's create two classes to represent a **ContactCard**: +上边的代码是一个**Client**类，**has_many**种联系人(contacts)，由于**ContactCard**类具有多态性，下一步，我们创建2个类来代表**ContractCard**： class Person < ActiveRecord::Base has_many :contact_cards, :as => :contact @@ -41,15 +39,13 @@ Next step in our example, let's create two classes to represent a **ContactCard* has_many :contact_cards, :as => :contact end -**Person** and **Business** relate to my **Client** class through the **ContactCard** table. In other words, I have two kinds of contacts, personal and business. - -This is not going to work, however. Watch what happens when I try to retrieve a contact: +**Person**和**Business**通过**ContactCard**表与**Client**类关联，换句话说，我有两类联系人，私人的(personal)和工作上的(business)。然而，这样做却行不通，看看当我试图获取一个contact时候发生了什么： >> Client.find(:first).contacts # ArgumentError: /…/active_support/core_ext/hash/keys.rb:48: # in `assert_valid_keys’: Unknown key(s): polymorphic -To make this work we have to use **:source_type**. Let's change our **Client** class: +为了让上述代码成功，我们需要使用**:source_type**。我们更改一下**Client**类： class Client < ActiveRecord::Base has_many :people_contacts, @@ -63,7 +59,7 @@ To make this work we have to use **:source_type**. Let's change our **Client** c :source_type => :business end -Notice how we now have two different ways of retrieving our contacts and we can say what contact **:source_type** we are expecting. +注意到现在我们有两种获得联系人的方式，我们可以选择我们期待哪种**:source_type**。 Client.find(:first).people_contacts Client.find(:first).business_contacts text/01_ActiveRecord/02_has_one.markdown @@ -1,8 +1,8 @@ ## Named_scope - -The *has\_finder* gem has been added to Rails with a different name: **named\_scope**. - -To fully understand what this adition brought to Rails let's look at the following examples: + +*has\_finder* gem已经添加到Rails当中了，有一个新名字**:named_scope**。 + +为了全面了解一下这为Rails带来了什么，我们看看下边的例子： class Article < ActiveRecord::Base named_scope :published, :conditions => {:published => true} @@ -14,7 +14,7 @@ To fully understand what this adition brought to Rails let's look at the followi Article.containing_the_letter_a.find(:first) Article.containing_the_letter_a.find(:all, :conditions => {…}) -Instead of creating a new method named **published** to return all published posts, I'm using a **named\_scope** to do it for me. But it can go even further than this. Let's look at another example of how it can be used: +通常我会创建一个新的叫做**published**的方法来返回所有的已经发布的帖子，不过在这里我是用了**named\_scope**来做同样的事情，而且还能得到其他的效果。看看另一个例子： named_scope :written_before, lambda { |time| { :conditions => ['written_on < ?', time] } @@ -31,11 +31,9 @@ Instead of creating a new method named **published** to return all published pos named_scope :multiple_extensions, :extend => [MultipleExtensionTwo, MultipleExtensionOne] -## Testing named\_scope with proxy\_options +## 用proxy\_options来测试named\_scope -**Named scopes** is a very interesting new feature for Rails 2.1, but after using it awhile you might have a hard time creating tests for more complex situations. - -Let's look at an example: +**Named scopes**是Rails 2.1中很有趣的新功能，不过使用一段时间以后你就会发现想创建一些复杂情况的测试会有点麻烦，看个例子： class Shirt < ActiveRecord::Base named_scope :colored, lambda { |color| @@ -43,9 +41,9 @@ Let's look at an example: } end -How to create a test that validates the generation of the scope ? +如何创建一个能测试scope结果的测试呢？ -To solve this issue, the method **proxy\_options** was created. It allows us to examine the options used in **named_scope**. To test the code above we could write: +为了解决这个问题，**proxy\_options**被创建了出来。它允许我们来检测**named_scope**使用的选项。为了测试上述代码，我们可以这样写测试： class ShirtTest < Test::Unit def test_colored_scope text/01_ActiveRecord/03_named_scope.markdown @@ -1,8 +1,8 @@ -## Increment and decrement +## Increment 和 decrement -**ActiveRecord**'s methods **increment**, **increment!**, **decrement** and **decrement!** can now take a new optional parameter. On previous verions of Rails you could use these methods to add or subtract 1 (one) from a given column. In Rails 2.1 you can tell which value that is to be added or subtracted. Like this: +**ActiveRecord**的方法**increment**,**increment!**,**decrement**和**descriment!**现在支持一个新的可选参数。之前版本的Rails中你可以通过这些方法指定的属性值加1或减1。在Rails 2.1中，你可以指定要增加或者减少的值，像这样： player1.increment!(:points, 5) player2.decrement!(:points, 2) -In the above example I am adding 5 points to player1 and subtracting 2 points from player2. Since this is an optional parameter, legacy code is not affected. \ No newline at end of file +上边的例子中，我向player1加了5分，从player2减了2分。由于这是一个可选的参数，所以之前的代码不会受到影响。 \ No newline at end of file text/01_ActiveRecord/04_increment_and_decrement.markdown @@ -2,29 +2,29 @@ ### Conditions -From now on, you can pass an object as a parameter to **ActiveRecord**'s **find** method. See this example: +从现在开始，你可以向**ActiveRecord**的**find**方法中传一个对象作为参数。看下边的例子： class Account < ActiveRecord::Base composed_of :balance, :class_name => "Money", :mapping => %w(balance amount) end - -In this case, you can pass an instance of **Money** as a parameter to the **find** method from the **Account** class, like this: + +这个例子中，你能向**Account**类的**find**方法中传入一个**Money**实例作为参数，像这样： amount = 500 currency = "USD" Account.find(:all, :conditions => { :balance => Money.new(amount, currency) }) ### Last - -Up to now we could only use three operators to look for data using **ActiveRecord**'s **find** method. These are: **:first**, **:all** and the object's own id (in this case whe don't pass any argument to **find** besides the id itself) -In Rails 2.1 there is a fourth operator named **:last**. A few examples: +到现在为止我们只能在**ActiveRecord**的**find**方法中使用三个操作符来查找数据，他们是**:first**,**:all**和对象自己的id(这种强况下，我们除了id以外不再传入其他的参数)。 + +在Rails 2.1当中，有了第四个操作符**:last**，几个例子： Person.find(:last) Person.find(:last, :conditions => [ "user_name = ?", user_name]) Person.find(:last, :order => "created_on DESC", :offset => 5) -To fully understand how this new operator works, just look at the following test: +为了能明白这个新的操作符如何工作，我们看看下边的测试： def test_find_last last = Developer.find :last @@ -32,26 +32,26 @@ To fully understand how this new operator works, just look at the following test end ### All - -The static method **all** is an alias to the also static **find(:all)**. Example: + +类方法**all**是另一个类方法**find(:all)**的别名。如： Topic.all is the same as Topic.find(:all) ### First -The static method **first** is an alias to the also static **find(:first)**. Example: +类方法**first**是另一个类方法**find(:first)**的别名。如： Topic.first is the same as Topic.find(:first) ### Last -The static method **last** is an alias to the also static **find(:last)**. Example: +类方法**last**是另一个类方法**find(:last)**的别名。如： Topic.last is the same as Topic.find(:last) -## Using **first** and **last** methods in named\_scope +## 在**named\_scope**中使用**first**和**last**方法 -All the methods mentioned above also work in **named\_scope**. Suppose we create a **named\_scope** named **recent**. The following is legal: +所有上述的方法同样适用于**named\_scope**。比如我们创建一个叫**recnet**的**named\_scope**，下列代码是有效的： post.comments.recent.last text/01_ActiveRecord/05_find.markdown @@ -1,11 +1,10 @@ ##Eager Loading -To explain this new funcionality, let's look at the following code: +为了解释这个新的功能，我们看如下代码： Author.find(:all, :include => [:posts, :comments]) -I'm searching through table **authors** and also including tables **posts** and **comments** in my query through the **author_id** column, which is the default column name according to Rails' convention for foreign_key names. -This search used to generate SQL queries like this: +我在查询**authors**这个表的记录，同时通过**author_id**包含进**posts**和**comments**表。这个查询原来会产生这样的sql查询语句： SELECT authors."id" AS t0_r0, @@ -24,12 +23,13 @@ This search used to generate SQL queries like this: LEFT OUTER JOIN posts ON posts.author_id = authors.id LEFT OUTER JOIN comments ON comments.author_id = authors.id -Exactly one long SQL query with **joins** between tables **authors**, **posts** and **comments**. We call this **cartesian product**. -This type of query is not always good performance-wise, so it was changed for Rails 2.1. The same query for **Author** class now uses a different approach to retrieve information from all three tables. Instead of using one SQL query with all three tables, Rails now uses three different queries - one for each table - which are shorter queries than the former that used to be generated. The result can be seen in the log after executing the previous ruby on rails code: +这个sql可真是够长的，在**authors**，**posts**和**comments**三个表之间用了joins。我们管这叫做笛卡尔乘积(**cartesian product**)。 + +这类查询往往在效率上边不高，所以在Rails 2.1中有了一些改进。同样的对于**Author**表的查询，现在使用了一种不同的方式从所有三个表当中取得信息。原来用了一条sql语句获得三个表记录，现在Rails用三条不同的查询语句，每个表一条，这要比之前生成的查询语句更短。新的结果可以在执行了上述代码后的log中看到： SELECT * FROM "authors" SELECT posts.* FROM "posts" WHERE (posts.author_id IN (1)) SELECT comments.* FROM "comments" WHERE (comments.author_id IN (1)) -In **most cases** three simpler queries will run faster than a complex and long query. +绝大多数情况下，三个简单的查询要比一个复杂的场查询语句执行的更快。 text/01_ActiveRecord/06_eager_loading.markdown @@ -1,7 +1,6 @@ ## Belongs_to - -The **belongs\_to** method was changed in order to allow the use of **:dependent => :destroy** and **:delete** in associations. -For example: + +为了能在关联中使用**:dependent=>:destroy**和**:delete**, **belongs\_to**方法做了一些更改，比如： belongs_to :author_address belongs_to :author_address, :dependent => :destroy text/01_ActiveRecord/07_belongs_to.markdown @@ -1,10 +1,10 @@ ## Polymorphic url -Helper methods for polymorphic URL are used as a more elegant solution to renamed routes when you're working with **ActiveRecord**. - -These methods come in handy when you want to generate the URL for a **RESTful** resource without specifying the type it is going to be associated with. - -It is very simple to work with them. Take a look at a few examples (commented out is how the same thing is done in versions of Rails prior to 2.1): +一些多态URL的辅助方法也被引入到新的Rails当中，用来提供一种更为简洁优雅的操作routes的方式。 + +这些方法在你想生成基于**RESTful**资源的URL，同时又不必显示指定资源的类型的时候，会现得十分有用。 + +使用方面，非常的简单，来看看一些例子（注释的部分是Rails 2.1之前的做法） record = Article.find(:first) polymorphic_url(record) #-> article_url(record) @@ -16,13 +16,13 @@ It is very simple to work with them. Take a look at a few examples (commented ou record = Comment.new polymorphic_url(record) #-> comments_url() -Notice how the **polymorphic_url** method is able to identify the type that is given to him and generates the correct routes. **Nested resources** and **namespaces** are also supported: +注意到**polymorphic_url**方法是如何确认传入参数的类型并且生成正确的routes。内嵌资源（**Nested resources**）和**namespaces**也同样支持： polymorphic_url([:admin, @article, @comment]) #-> this will return: admin_article_comment_url(@article, @comment) -You can also use prefixes such as **new**, **edit** and **formatted**. Take a look at a few examples: +你同样能够使用**new**, **edit**, **formatted**等前缀。看看下边的例子： edit_polymorphic_path(@post) #=> /posts/1/edit text/01_ActiveRecord/08_polymorphic_url.markdown @@ -1,6 +1,6 @@ -## Readonly relationships +## 只读关联 (Readonly relationships) -A new feature is added to the relationship among models. To avoid change in a models' state you can now use **:readonly** when describing associations. Let's take a look at a few examples: +一个新的功能被添加到了models之间的关联当中。为了避免更改关联模型的状态，你现在可以使用**:readonly**来描述一个关联。我们看几个例子： has_many :reports, :readonly => true @@ -10,4 +10,4 @@ A new feature is added to the relationship among models. To avoid change in a mo has_and_belongs_to_many :categories, :readonly => true -This way your associated models are safe from being edited from within this model. If you try editing any of them you will get an **ActiveRecord::ReadOnlyRecord** exception. \ No newline at end of file +这样，关联的models就能够避免在model中被更改，如果试图更改他们，那么将得到一个**ActiveRecord::ReadOnlyRecord**异常 \ No newline at end of file text/01_ActiveRecord/09_readonly.markdown @@ -1,6 +1,6 @@ -## Methods add\_timestamps and remove\_timestamps +## add\_timestamps和remove\_timestamps方法 -We now have two new methods: **add\_timestamps** and **remove\_timestamps**. They add and remove, respectively, **timestamp** columns. Let's take a look at an example: +现在我们有两个新的方法**add\_timestamps**和**remove\_timestamps**，他们分别添加，删除**timestamp**列。看个例子： def self.up add_timestamps :feeds text/01_ActiveRecord/10_migration.markdown @@ -1,6 +1,6 @@ ## Calculations -**ActiveRecord::Calculations** has changed a bit to support table names. This comes in handy when we have relationships among different tables with the same column name. You have these two options now: +**ActiveRecord::Calculations**做了一些更改以支持数据库表名。这个功能在几个不同表之间存在关联且相关列名相同时会非常有用。我们有两个选项可选： authors.categories.maximum(:id) authors.categories.maximum("categories.id") text/01_ActiveRecord/11_calculations.markdown @@ -1,13 +1,13 @@ -## ActiveRecord::Base.create accepts blocks +## ActiveRecord::Base.create接受blocks -We are already used to **ActiveRecord::Base.new** accepting blocks. Now we can do the same thing in the **create** method: +我们已经习惯了**ActiveRecord::Base.new**接受block作为参数了，现在**create**也同样接受blocks了： # Creating an object and passing it a block describing its attributes User.create(:first_name => 'Jamie') do |u| u.is_admin = false end -We can also use the same method to create many objects at once: +我们也能用同样的方法一次创建多个对象： # Creating an array of new objects using a block. # The block is executed once for each of object that is created. @@ -15,11 +15,11 @@ We can also use the same method to create many objects at once: u.is_admin = false end -And it also works with associations: +同样在关联当中可以使用： author.posts.create!(:title => "New on Edge") {|p| p.body = "More cool stuff!"} - # ou + # or author.posts.create!(:title => "New on Edge") do |p| p.body = "More cool stuff!" text/01_ActiveRecord/12_blocos.markdown @@ -1,8 +1,8 @@ ## change\_table -The creation of **migrations** in Rails 2.0 was a lot sexier than on previous verions, but to alter a table using **migrations** was not sexy at all. +在Rails 2.0当中，创建的**migrations**要比之前版本更为性感，不过要想用**migrations**修改一个表可就不那么性感了。 -In Rails 2.1, alter table became also sexy with the new method **change\_table**. Let's take a look at an example: +在Rails 2.1中，修改表也由于新方法**change\_table**而变得同样性感了。我们来看个例子： change_table :videos do |t| t.timestamps # this adds columns created_at and updated_at @@ -11,7 +11,7 @@ In Rails 2.1, alter table became also sexy with the new method **change\_table** t.remove :name, :email # this removes columns name and email end -The new method **change\_table** works just like his cousin **create\_table** but instead of creating a new table it just alters an already existing table by adding or removing columns and indexes. +新方法**change\_table**的使用就和他的表兄**create\_table**一样，只不过不是创建一个新表，而是通过添加或者删除列或索引来更改现有的表。 change_table :table do |t| t.column # adds an ordinary column. Ex: t.column(:name, :string) text/01_ActiveRecord/13_change_table.markdown @@ -1,6 +1,6 @@ ## Dirty Objects -Now in Rails we are able to keep track of changes made to **ActiveRecord**. It is possible to know if an object has been changed or not. In case it has been changed, we can track down its latest changes. Let's take look at a few examples: +在新Rails当中，我们同样可以跟踪对**ActiveRecord**所做的更改。我们能够知道是否一个对象被进行了修改，如果有更改，那么我们就能跟踪到最新的更改。我们来看几个例子： article = Article.find(:first) article.changed? #=> false @@ -15,7 +15,7 @@ Now in Rails we are able to keep track of changes made to **ActiveRecord**. It i # before and after the change article.title_change #=> ["Title", "New Title"] -As you can see it is very simple. You can also list all changes made to the object in one of two ways: +可以看到，使用上边非常的简单，同时你也能够通过下列两种方法的任意一种列出对一个对象的所有更改： # returns a list with all of the attributes that were changed article.changed #=> ['title'] @@ -24,13 +24,13 @@ As you can see it is very simple. You can also list all changes made to the obje # along with its values before and after article.changes #=> { 'title’ => ["Title", "New Title"] } -Notice that when an object is saved, its status changes: +注意到当一个对象被保存后，他的状态也随之改变： article.changed? #=> true article.save #=> true article.changed? #=> false -In case you want to change an object's state without using **attr=**, you will need to explicitly inform that the attribute was changed by using the method **attr\_name\_will\_change!** (replace **attr** with an object's real attribute). Let's look at one last example: +如果你不通过**attr=**来更改一个对象的状态，那么你需要显示的调用**attr\_name\_will\_change!**方法(用对象的实际属性名称替换**attr**)来通知属性已经被更改。我们再看最后一个例子： article = Article.find(:first) article.title_will_change! text/01_ActiveRecord/14_dirty_objects.markdown @@ -1,12 +1,12 @@ ## Partial Updates -The implementation of **Dirty Objects** was the starting point for another very interesting feature. - -Since we can now track down what has changed in an object's state, why not use it to avoid unnecessary updates to the database ? - -On previous versions of Rails when we called **save** from an already existing **ActiveRecord** object, all of its fields would be updated in the database. Even the ones that had not suffered any change. +**Dirty Objects**的实现让另一个非常有趣的功能变为可能。 -This action could be greatly enhanced with the use of **Dirty Objects** and it is exactly what happened. Take a look at the SQL query generated in Rails 2.1 when trying to save an object that suffered a slight change: +由于我们现在可以跟踪一个对象的状态是否发生改变，那么为什么不用它来避免那些不必要的对数据裤的更新呢？ + +在之前版本的Rails当中，当我们对一个已经存在的**ActiveRecord**对象调用**save**方法的时候，所有数据库中的字段都会被更新，即使那些没有做任何更改的字段。 + +这种方式在使用了Dirty Objects以后应该会有很大的改进，而实际情况也的确如此。看看在保存一个有一点更改的对象时，Rails 2.1生成的SQL查询语句： article = Article.find(:first) article.title #=> "Title" @@ -19,19 +19,19 @@ This action could be greatly enhanced with the use of **Dirty Objects** and it i article.save #=> "UPDATE articles SET title = 'New Title' WHERE id = 1" -Notice how only the fields that were changed in the application were updated in the database. If no field had been updated in the application, then **ActiveRecord** would not execute any update. - -To enable/disable this new feature you change the **partial\_updates** property related to your model. +注意到，只有那些在应用中被更改的属性才在被更新。如果没有属性被更改，那么**ActiveRecord**就不执行任何更新语句。 + +为了开启/关闭这个新功能，你要更改model的**partial\_updates**属性。 # To enable it MyClass.partial_updates = true -If you wish to enable/disable this feature to all of your models, then you must edit the file *config/initializers/new\_rails\_defaults.rb*: +如果希望对所有的models开启/关闭这个功能，那么你必须编辑*config/initializers/new\_rails\_defaults.rb*： # Enable it to all models ActiveRecord::Base.partial_updates = true -Don't forget to also inform Rails through *config/initializers/new\_rails\_defaults.rb* if you plan to edit a field without using the method **attr=**, like this: +别忘了如果你不通过attr=更改字段，同样要通过*config/initializers/new\_rails\_defaults.rb*来通知Rails，像这样: # If you use **attr=**, # then it's ok not informing @@ -45,4 +45,4 @@ Don't forget to also inform Rails through *config/initializers/new\_rails\_defau person.name << 'by' person.name_change # => ['bob', 'bobby'] -If you don't inform changes like these will be occurring, then they won't be able to be tracked down and your database table won't be correctly updated. +如果你不通知Rails，那么上述的代码同样会更改对象的属性，但是却不能被跟踪到，从而也就无法正确的更新数据库中的相应字段。 \ No newline at end of file text/01_ActiveRecord/15_partial_updates.markdown @@ -1,6 +1,6 @@ -## Smallint, int or bigint in MySQL? +## MySQL中使用Smallint, int还是bigint？ -The **MySQL** adapter for **ActiveRecord** is now smarter when creating or altering columns in the database using integer types. According to the option **:limit**, it will now tell if the column will be a **smallint**, **int** or **bigint**. Let's take a look at an example that does just that: +现在在创建或者更改整型列的时候**ActiveRecord**的**MySQL**适配器会处理的更为聪明，它可以根据**:limit**属性确定一个字段的类型应该是**smallint**，**int**还是**bigint**。我们来看个实现上述功能的例子： case limit when 0..3 @@ -13,7 +13,7 @@ The **MySQL** adapter for **ActiveRecord** is now smarter when creating or alter 'int(11)' end -Now let's map it in a **migration** file and see what column type will be created for each column: +现在我们在**migration**中使用它，看看每一个字段应该匹配什么类型： create_table :table_name, :force => true do |t| @@ -30,4 +30,4 @@ Now let's map it in a **migration** file and see what column type will be create t.integer :column_four # int(11) end -The **PostgreSQL** adapter had this feature already and **MySQL** just caught up. +**PostgreSQL**适配器已经有这个功能了，现在**MySQL**也不甘落后了。 \ No newline at end of file text/01_ActiveRecord/16_mysql.markdown @@ -1,9 +1,9 @@ -## Option :select in has\_one and belongs\_to +## has\_one和belongs\_to中的:select选项 -The already known methods **has\_one** and **belongs\_to** just got a now option: **:select**. +已经为人熟知的**has\_one**和**belongs\_to**方法现在接收一个新属性**:select**。 -Its default value is "*" (as in "SELECT * FROM table"), but you can edit it to retrieve only the columns you are going to be using. - -Don't forget to include the **primary** and **foreign keys**, otherwise you will get an error. +它的默认值是“*”(正如"SELECT * FROM table")，不过你可以更改默认值来获得任何你希望的列。 -The **belongs_to** method does not have the option **:order** anymore. But don't worry, because it didn't really have a use. +别忘了包括进主键和外键，否则你会得到一个错误。 + +**belongs_to**方法不再支持**:order**选项了，不过不要担心，因为那基本上没什么用处。 \ No newline at end of file text/01_ActiveRecord/17_select_has_many.markdown @@ -1,6 +1,6 @@ -## Storing the complete name of a class when using STI +## 使用单表继承(STI)的时候存储类的全名 -Whenever we use **models** with **namespace** and **STI**, **ActiveRecord** stores just the name of the class, without its **namespace** (*demodulized*). This will only work when all of the classes in the **STI** are in the same **namespace**. Let's look at an example: +当我们的**models**有**namespace**，并且是单表继承(STI)的时候，**ActiveRecord**仅仅将类名，而不是包括n**amespace**(**demodulized**)在内的全名存起来。这种情况仅仅当单表继承的所有类在一个**namespace**的时候有效，看个例子： class CollectionItem < ActiveRecord::Base; end class ComicCollection::Item < CollectionItem; end @@ -12,10 +12,9 @@ Whenever we use **models** with **namespace** and **STI**, **ActiveRecord** stor # returns an error, because it can't find # the class Item -This change adds a new option that makes **ActiveRecord** store the whole name of the class - -To enable/disable this feature, you should include or edit the following in your **environment.rb**. +新的Rails添加了一个属性，从而使**ActiveRecord**能存储类的全名。 +可以在**environment.rb**当中添加如下代码来启动/关闭这个功能： ActiveRecord::Base.store_full_sti_class = true -Its default value is true. \ No newline at end of file +默认值是true。 \ No newline at end of file text/01_ActiveRecord/18_sti.markdown @@ -1,6 +1,6 @@ -## Method table_exists? +##table_exists?方法 -New method for the **AbstractAdapter** class: **table\_exists**. It is very simple to use: +**AbstractAdapter**类有个新方法**table\_exists**，用法非常简单： >> ActiveRecord::Base.connection.table_exists?("users") => true text/01_ActiveRecord/19_tables_exists.markdown @@ -1,20 +1,20 @@ -## Timestamped Migrations +## 基于时间戳的Migrations (Timestamped Migrations) -When you are just starting Rails or developing something on your own, **migrations** seem to be the best solution to all of your problems. However, when with a team of developers on a project, you will find out (if you haven't already) that it becomes a bit more troublesome to handle race conditions on migrations. The new timestamped migrations in Rails 2.1 to the rescue. +当你一个人使用Rails开发的时候，**migrations**似乎是所有问题的最好解决方案。不过，当和团队的其他成员共同开发一个项目的时候，你就会发现(如果你尚未发现)处理**migrations**同步的问题非常棘手。Rails 2.1中基于时间戳的**migrations**解决方案很好的解决了这个问题。 -Before the introduction of **timestamped migrations**, each new migration created had a number which prefaced the migration name. If two migrations were generated by different developers and not committed instantly, they could end up having the same number preface by different migration info. At this point your schema_info is out of date and you have a conflict in your source control. - -There were many ways to "try" to solve this problem. Many plugins were created with different approaches to solve this issue. Despite the plugins available, one thing was clear: the old way simply didn't work. +在基于时间戳的**migrations**引入之前，创建每一个migration都会在其名字之前生成一个数字，如果两个**migrations**分别由两个开发者生成，并且都没有即时的提交到版本库中，那么最后就有可能存在相同前缀数字，但是不同内容的**migrations**，这时你的schema_info表就会过期，同时在版本控制系统中出现冲突。 -If you were using Git, then you would be digging an even deeper hole, since your team would probably have a couple of working branches and out-of-date **migrations** in all of them. You would have serious conflict problems when merging branches. - -To solve this huge problem, the core team changed how **migrations** works in Rails. Instead of prefacing each migration file with a number from corresponding to the current schema_info's version count, it is now prefaced with a string based on the **UTC** time and following the format YYYYMMDDHHMMSS. +试图解决这个问题的尝试有很多，人们创建了很多plugins以不同的方式解决这个问题。尽管有一些plugins可用，不过一点是非常清楚的，旧的方式不能满足我们的要求了。 -Also a new table called **schema_migrations** was created and it stores which **migrations** that have already been executed. That way, if anyone creates a **migration** with a smaller number, rails will **rollback** migrations until the previous version and then run everything up to the current version. +如果你使用Git，那么你可能在给自己挖一个更大的陷阱，因为你的团队可能同时有几个working branches，过期了的migrations则在每一个branch中都存在。这样当合并这些branches的时候就会有严重的冲突问题。 -Apparently, it solves the conflict problem with **migrations**. +为了解决这个大问题，Rails核心团队已经改变了**migrations**的工作方式。他们废弃了原有的以当前schema_info中version列的值作为migration前缀的依据的方法，取而代之的是基于**UTC**时间，按照YYYYMMDDHHMMSS格式的字符串表达方式作为前缀。 -There are also two new rake tasks to "walk through" **migrations**: +同时创建了一个新的叫**schema_migrations**的表，表中存着哪些**migrations**已经被执行了，这样如果发现有人创建了一个有较小值的**migration**，rails会回滚**migrations**到之前的那个版本，然后重新执行所有的**migration**直到当前的版本。 + +显然，这样做解决了migrations带来的冲突问题。 + +有两个新的和**migrations**相关的rake命令： rake db:migrate:up rake db:migrate:down text/01_ActiveRecord/20_utc_migrations.markdown 2c0b20c50e9e90d2cb9e8603189791229109a4c8 Libin Pan libin.pan@gmail.com http://github.com/libin/rails21-book-cn/commit/80c4507313cea9d6db44ad438877da6d61ab0c20 80c4507313cea9d6db44ad438877da6d61ab0c20 2008-06-21T14:24:25-07:00 2008-06-21T14:24:25-07:00 2 done, 12 to go b7e764e562e9c3e5ca954b3521f46ac064ab83ec Libin Pan libin.pan@gmail.com