《Programming Ruby 3.2》beta版：早期获取与反馈

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《Programming Ruby 3.2：The Pragmatic Programmers' Guide》是由Noel Rappin 和 Dave Thomas 联合编写的，这本书是Pragmatic Bookshelf于2023年推出的一款技术书籍。作为"beta book"的一部分，作者们在正式出版前向读者提供了早期版本，以便获取反馈，提升内容质量。这本书的特点在于它的实时更新性和开放性，读者可以在beta阶段获得内容，比常规出版时间提前几个月。然而，需要明确的是，由于处于开发中的状态，这本书尚未经过全面的技术编辑和校对，因此可能会存在一些问题。内容可能包含未修正的技术错误、拼写错误、语法不规范以及排版问题，如糟糕的页面分隔、过长的代码行、不正确的断词等。此外，书中尚未创建索引，使用时可能存在不便。尽管存在这些缺陷，但作者们相信读者在探索过程中仍能从中获益。为了确保读者能够跟随最新进展，Pragmatic Bookshelf的用户可以通过账户访问并下载更新的电子书。当书本最终完成时，用户将获得最终版本，这表明作者团队对于读者参与和反馈的重视。《Programming Ruby 3.2》是一本具有互动性和实验性质的编程指南，适合那些希望紧跟Ruby 3.2语言发展，并愿意接受一些初期瑕疵的程序员。尽管它不是传统的成品，但其开放的开发过程使得它成为学习者了解新技术和发展趋势的独特资源。

Part I

Facets of Ruby

Welcome to Ruby! This section is a tutorial through all the Ruby

you’ll need to be able to understand a good-sized Ruby application.

We’ll cover the most important parts of the syntax and the stan-

dard library, and go beyond the basics in a couple of places where

Ruby has a particularly interesting or powerful tool at hand.

CHAPTER 1

Getting Started

We’re going to spend a lot of time in this book talking about the Ruby language. Before we

do, we want to make sure you can get Ruby installed and running on your computer. That

way, you can try sample code and experiment on your own as you read along. If you want

to learn Ruby you should get into the habit of writing code as you are reading.

If you are not comfortable with using a command line, we can help. Please turn to Appendix

3, Command-Line Basics, and we will give you all the information you need to get started.

Installing Ruby

There’s a good chance your operating system already has Ruby installed. Try typing

ruby --

version

at a command prompt—you may be pleasantly surprised. Likely, though, you’ll find

that the Ruby version is out of date. For example, as this is being written, macOS ships with

Ruby 2.6.10, which is multiple versions behind the current Ruby.

The examples in this book are written against Ruby 3.2. While most of the code will work

in older versions of Ruby, for performance and security reasons you should try to get on the

most current version.

You can install Ruby in a variety of different ways, so providing general installation

instructions becomes a little bit of a choose-your-own-adventure story. Most of the examples

in this book assume you are using a Linux or Unix style system that responds to Linux-style

commands. This includes all Linux distributions, macOS, Windows systems running Windows

Subsystem for Linux (WSL)

, and most Docker

containers as well as cloud-based development

environments such as Replit.

That said, Ruby does run on Windows. The process for managing a Ruby installation on

Windows is different, and we’ll cover it in full detail later in this chapter.

Please note that the tooling around Ruby installation does change frequently, and some of

the specific instructions might be out of date, or replaced by newer tools.

https://docs.microsoft.com/en-us/windows/wsl/install

https://www.docker.com

https://replit.com

report erratum • discuss

Opting Out of Installation

If you don’t want to install anything on your computer for some reason, you

can take advantage of cloud-based development environments such as Replit

or GitHub Codespaces. These environments enable you to write your code in

a browser and run it against a cloud-based virtual machine.

Installing Ruby with the rbenv Version Manager

In order to facilitate our installation of Ruby, we are going to use a version manager, which

is a tool that allows you to install and switch between multiple Ruby versions on the same

machine. There are many reasons to use a version manager to handle your Ruby installation.

Being able to easily switch between multiple versions of Ruby gives you the flexibility to

work with multiple projects that might have been written at different times. In addition, the

version managers have been created for easy installation, so installing multiple Ruby versions

with a version manager is easier than installing a single version by itself. More powerful

and easier to use is a hard combination to beat. If you are interested in just downloading

one version of Ruby, you can find system-by-system instructions at

https://www.ruby-lang.org/

en/documentation/installation

The tool we are going to use in this book is called rbenv.

Rbenv is not the only Ruby version

manager, but it’s probably the most commonly used these days. Other commonly used

version managers are RVM

and chruby.

(And yes, having competing tools named “RVM”

and “rbenv” is confusing.) If you are using version management for multiple languages,

you might want to look at a project called asdf, which unifies different languages’ version

managers,

and is rapidly becoming more popular within Ruby.

We will install rbenv through the conveniently provided rbenv-installer program. If executing

somebody else’s shell script makes you nervous, you can inspect the script at

https://github.com/

rbenv/rbenv-installer/blob/main/bin/rbenv-installer

before you run it.

From a command terminal, enter this command all on one line (the line is split here for page-

width reasons):

$ curl -fsSL

https://github.com/rbenv/rbenv-installer/raw/HEAD/bin/rbenv-installer | bash

Curl is a command-line tool for accessing URLs and doing something useful with the return

value—in this case, retrieving a shell script from the rbenv GitHub repo and passing it along

to a bash shell to be executed.

This script will install rbenv using the appropriate package manager for your system, and

will also install a helper program called ruby-build that will manage the download and

installation of different Ruby versions.

The installation command might produce a lot of output—especially if you are on a macOS

system that uses the Homebrew package manager. On a Mac, it should end with the following,

a Windows user under WSL might see something different:

https://github.com/rbenv/rbenv

https://rvm.io

https://github.com/postmodern/chruby

https://asdf-vm.com

Chapter 1. Getting Started • 4

report erratum • discuss

All done! Note that this installer does NOT edit your shell configuration files: 1. Run `rbenv init' to view

instructions on how to configure rbenv for your shell. 2. Launch a new terminal window after editing shell

configuration files.

Following instructions, run

rbenv init

. This is the output on a Mac running zshell (your

instructions may be different):

$ rbenv init

# Load rbenv automatically by appending

# the following to ~/.zshrc:

eval "$(rbenv init - zsh)"

No matter what your setup is, what you should get in this instruction is:

• The file that contains the shell configuration you need to update

• The text you need to put at the end of the file

You need to put the suggested line of text at the end of your configuration file and open a

new terminal window – the change only takes effect when a window is loaded, so the easiest

way to get rbenv started is to open a new terminal window. Again, if you have any questions

about how to use the terminal, see Appendix 3, Command-Line Basics.

Now, let’s install a specific Ruby version.

Installing Rubies with rbenv

Rbenv allows you to see a list of the Ruby versions you are most likely to want to install

with the command

rbenv install -l

. Here’s the list as of today:

$ rbenv install -l

2.7.7

3.0.5

3.1.3

3.2.0

jruby-9.4.0.0

mruby-3.1.0

picoruby-3.0.0

rbx-5.0

truffleruby-22.3.0

truffleruby+graalvm-22.3.0

Only latest stable releases for each Ruby implementation are shown.

Use 'rbenv install --list-all / -L' to show all local versions.

This list is the most current patch version of various Ruby implementations. You can see

Ruby versions for the main Ruby implementation version 2.7, 3.0, 3.1, and 3.2. (When talking

about different Ruby implementations, the main one is sometimes called CRuby, and

sometimes called MRI, for “Matz’s Ruby Interpreter.”) There are also other versions we’re

not going to talk about much here. JRuby

is a Ruby version that runs on the Java Virtual

Machine, mruby is a special limited build of Ruby for running on embedded hardware. Rbx

is Rubinius, a defunct project to implement Ruby in Ruby, and TruffleRuby

is an implemen-

tation of the language that is focused on high performance.

https://www.jruby.org

https://github.com/oracle/truffleruby

report erratum • discuss

Installing Ruby • 5

Our interest right now is Ruby 3.2.0, which we can install with the command

rbenv install

3.2.0

. If you don’t see the most current version of Ruby on the list, and you’ve installed rbenv

previously, you may get instructions on how to update ruby-build to get newer Ruby versions

in your list. Note that none of the rbenv commands require us to have superuser access or

to use

sudo

. One of the joys of the Ruby version managers, including rbenv, is that they do

everything inside your home directory—you don’t have have any special system privileges

to install or use new Ruby versions.

$ rbenv install 3.2.0

To follow progress, use

'tail -f <REDACTED>'

or pass --verbose

Installing openssl-3.0.7...

Installed openssl-3.0.7 to /Users/noel/.rbenv/versions/3.2.0

Installing ruby-3.2.0...

ruby-build: using readline from homebrew

ruby-build: using gmp from homebrew

Installed ruby-3.2.0 to /Users/noel/.rbenv/versions/3.2.0

Your output may be slightly different, depending on the exact version number and whether

you are re-installing the Ruby version.

We can verify that the Ruby version has been installed with

rbenv versions

, for example

$ rbenv versions

* system

3.2.0

The

system

here is the pre-defined Ruby for the operating system if such a thing exists, and

the asterisk shows which version is currently active.

An important step: after you install a new ruby via rbenv, you must run the command

rbenv

rehash

. This command produces no output, but it does enable rbenv to use the newly installed

Ruby.

Right now, the system Ruby is still active. Let’s change that.

Switching Rubies with rbenv

This is where we start to see the payoff. Once different Ruby versions are installed, and

rbenv

rehash

has been called, Rbenv allows us multiple ways to switch the Ruby version we are

using.

The command

rbenv local <version>

changes the Ruby version for the directory you are in:

$ ruby --version

ruby 2.6.10p210 (2022-04-12 revision 67958) [universal.arm64e-darwin22]

$ rbenv local 3.2.0

$ ruby --version

ruby 3.2.0 (2022-12-25 revision a528908271) [arm64-darwin22]

This setting for the directory persists even if you leave the directory and come back. (If you

don’t want the change to persist beyond the current session, you can use

rbenv shell <version>

)

instead of

rbenv local

Chapter 1. Getting Started • 6

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