Rails 4敏捷Web开发指南：适应最新版本与技术

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"《敏捷Web开发与Rails,第4版》是一本专注于Ruby on Rails（Rails）框架的教程，适用于Rails 3版本。该书强调了在快速变化的IT行业中采用敏捷开发方法来构建Web应用。Rails是一个开源的Web应用程序框架，以其简洁的语法和约定优于配置的原则而闻名。书中内容涵盖了Rails的核心概念、模型-视图-控制器（MVC）架构、数据库集成、路由、模板引擎等，适合初学者和有经验的开发者深入学习。由于Rails团队不断进行迭代更新，可能会导致与旧版本不兼容，因此作者强调读者应安装书中指定的Rails 3版本，以便正确运行示例代码。通过命令行中的`rails -v`可以检查当前正在使用的Rails版本。作者提醒读者注意，书中提供的信息可能与后续版本的Rails有所不同，为了获取关于Rails更新对本书内容影响的最新资讯，读者可以访问Rails官方文档（<http://www.rubyonrails.org/>），或者查看Rails官方博客和社区论坛，以便及时适应框架的最新发展。 Linux公社（LinuxIDC.com）作为一个知名的Linux技术网站，提供了关于Ubuntu、Fedora、SUSE等Linux发行版的教程和资讯，同时也设有针对红旗Linux和Android的专业栏目，为用户提供丰富的IT教育资源。然而，站内内容并不一定代表官方立场，仅仅是为用户提供更多信息，不构成技术建议。该网站还提供了广告服务、网站地图、帮助信息和联系方式，以及版权声明。《Agile Web Development with Rails, 4th Edition》不仅是一本技术指南，也体现了当时敏捷开发的最佳实践，对于希望利用Rails进行高效Web开发的读者来说，是不可或缺的学习资源。"

ACKNOWLEDGMENTS 15

Finally, the Rails core team has been incredibly helpful, answering questions,

checking out code fragments, and ﬁxing bugs. A big “thank you” to the follow-

ing:

Scott Barron (htonl), Jamis Buck (minam), Thomas Fuchs (madrobby),

Jeremy Kemper (bitsweat), Y e h u d a Katz (wycats),

Michael Koziarski (nzkoz), Marcel Molina Jr, (noradio),

Rick Olson (technoweenie), Nicholas Seckar (Ulysses),

Sam Stephenson (sam), Tobias Lütke (xal), José V a l i m (josevalim), and

Florian W e b e r (csshsh)

Sam Ruby

March 2011

rubys@intertwingly.net

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RAILSSIMPLYFEELSRIGHT 17

Rails applications are written in Ruby, a modern, object-oriented scripting

language. Ruby is concise without being unintelligibly terse—you can express

ideas naturally and cleanly in Ruby code. This leads to programs that are easy

to write and (just as important) are easy to read months later.

Rails takes Ruby to the limit, extending it in novel ways that make a pro-

grammer’s life easier. This makes our programs shorter and more readable.

It also allows us to perform tasks that would normally be done in external

conﬁguration ﬁles inside the codebase instead. This makes it far easier to see

what’s happening. The following code deﬁnes the model class for a project.

Don’t worry about the details for now. Instead, just think about how much

information is being expressed in a few lines of code.

class Project < ActiveRecord::Base

belongs_to :portfolio

has_one :project_manager

has_many :milestones

has_many :deliverables, :through => :milestones

validates :name, :description, :presence => true

validates :non_disclosure_agreement, :acceptance => true

validates :short_name, :uniqueness => true

end

Two other philosophical underpinnings keep Rails code short and readable:

DRY and convention over conﬁguration. DRY stands for don’t r e p e a t yourself :

every piece of knowledge in a system should be expressed in just one place.

Rails uses the power of Ruby to bring that to life. Y o u ’ l l ﬁnd very little duplica-

tion in a Rails application; you say what you need to say in one place—a place

often suggested by the conventions of the MVC architecture—and then move

on. For programmers used to other web frameworks, where a simple change

to the schema could involve them in half a dozen or more code changes, this

was a revelation.

Convention over conﬁguration is crucial, too. It means that Rails has sensi-

ble defaults for just about every aspect of knitting together your application.

Follow the conventions, and you can write a Rails application using less code

than a typical Java web application uses in XML conﬁguration. If you need to

override the conventions, Rails makes that easy, too.

Developers coming to Rails found something else, too. Rails isn’t playing catch-

up with the new de facto web standards; it’s helping deﬁne them. And Rails

makes it easy for developers to integrate features such as Ajax and RESTful

interfaces into their code, because support is built in. (And if you’re not famil-

iar with Ajax and REST interfaces, never fear—we’ll explain them later in the

book.)

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RAILSIS AGILE 18

Developers are worried about deployment too. They found that with Rails you

can deploy successive releases of your application to any number of servers

with a single command (and roll them back equally easily should the release

prove to be somewhat less than perfect).

Rails was extracted from a real-world, commercial application. It turns out

that the best way to create a framework is to ﬁnd the central themes in a

speciﬁc application and then bottle them up in a generic foundation of code.

When you’re developing your Rails application, you’re starting with half of a

really good application already in place.

But there’s something else to Rails—something that’s hard to describe. Some-

how, it just feels right. Of course, you’ll have to take our word for that until

you write some Rails applications for yourself (which should be in the next

forty-ﬁve minutes or so...). That’s what this book is all about.

Rails Is Agile

The title of this book is Agile W e b Development with Rails. Y o u may be sur-

prised to discover that we don’t have explicit sections on applying agile prac-

tices X, Y , and Z to Rails coding.

The reason is both simple and subtle. Agility is part of the fabric of Rails.

Let’s look at the values expressed in the Agile Manifesto as a set of four pref-

erences:

• Individuals and interactions over processes and tools

• W o r k i n g software over comprehensive documentation

• Customer collaboration over contract negotiation

• Responding to change over following a plan

Rails is all about individuals and interactions. There are no heavy toolsets,

no complex conﬁgurations, and no elaborate processes. There are just small

groups of developers, their favorite editors, and chunks of Ruby code. This

leads to transparency; what the developers do is reﬂected immediately in what

the customer sees. It’s an intrinsically interactive process.

Rails doesn’t denounce documentation. Rails makes it trivially easy to cre-

ate HTML documentation for your entire codebase. But the Rails development

process isn’t driven by documents. Y o u won’t ﬁnd 500-page speciﬁcations at

the heart of a Rails project. Instead, you’ll ﬁnd a group of users and devel-

opers jointly exploring their need and the possible ways of answering that

need. Y o u ’ l l ﬁnd solutions that change as both the developers and the users

become more experienced with the problems they’re trying to solve. Y o u ’ l l ﬁnd

1. http://agilemanifesto.org/. Dave Thomas was one of the seventeen authors of this document.

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WHOTHISBOOKIS FOR 19

a framework that delivers working software early in the development cycle.

This software may be rough around the edges, but it lets the users start to get

a glimpse of what you’ll be delivering.

In this way, Rails encourages customer collaboration. When customers see

just how quickly a Rails project can respond to change, they start to trust

that the team can deliver what’s required, not just what has been requested.

Confrontations are replaced by “What if?” sessions.

That’s all tied to the idea of being able to respond to change. The strong, almost

obsessive, way that Rails honors the DRY principle means that changes to

Rails applications impact a lot less code than the same changes would in other

frameworks. And since Rails applications are written in Ruby, where concepts

can be expressed accurately and concisely, changes tend to be localized and

easy to write. The deep emphasis on both unit and functional testing, along

with support for test ﬁxtures and stubs during testing, gives developers the

safety net they need when making those changes. W i t h a good set of tests in

place, changes are less nerve-racking.

Rather than constantly trying to tie Rails processes to the agile principles,

we’ve decided to let the framework speak for itself. As you read through the

tutorial chapters, try to imagine yourself developing web applications this way:

working alongside your customers and jointly determining priorities and solu-

tions to problems. Then, as you read the more advanced concepts that follow

in Part III, see how the underlying structure of Rails can enable you to meet

your customers’ needs faster and with less ceremony.

One last point about agility and Rails: although it’s probably unprofessional

to mention this, think how much fun the coding will be.

Who This Book Is For

This book is for programmers looking to build and deploy web-based applica-

tions. This includes application programmers who are new to Rails (and per-

haps even new to Ruby) and ones who are familiar with the basics but want a

Rails 4敏捷Web开发指南：适应最新版本与技术

Agile Web Development with Rails (4th edition) .pdf

Agile Web Development with Rails (4th edition).pdf

Agile Web Development with Rails 4th(正式版).pdf

agile web development with rails 4th edition 源代码

Agile Web Development with Rails 4th edition（敏捷Web开发与Rails:程序指南 第四版）

Agile Web Development with Rails 4th -Final Edition

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Agile Web Development with Rails (4th edition)

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(应用Rails进行敏捷Web开发(第4版) Agile.Web.Development.with.Rails.4th.Edition 原版

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Agile Web Development with Rails 4th edition（敏捷Web开发与Rails:程序指南第四版）