Ruby Pocket Reference

### Ruby Pocket Reference Key Points **Title and Description Overview:** The "Ruby Pocket Reference" by Michael Fitzgerald is a concise and practical guide designed to serve as a quick reference for Ruby programmers. Published in its first edition in July 2007 by O'Reilly Media, this book packs 176 pages full of essential Ruby knowledge. It is part of the Pocket References series, which is known for providing succinct and focused information on various programming languages and technologies. The book is structured to provide quick access to critical Ruby concepts and syntax, making it ideal for developers who are already familiar with the language but need a handy resource to refresh their memory or look up specific details. Whether you are using Ruby for web development through the Rails framework or other applications, this pocket reference aims to be your go-to guide. **Key Knowledge Points:** #### Running Ruby - **Running the Ruby Interpreter:** The book starts by explaining how to run the Ruby interpreter, which is the command-line interface used to execute Ruby code. This section covers the basics of running Ruby scripts and provides insights into common command-line options and arguments. - **Using a Shebang Line on Unix/Linux:** For Unix/Linux users, the book explains how to use the shebang line (`#!/usr/bin/env ruby`) at the beginning of a Ruby script file. This line tells the system to run the script using the Ruby interpreter. - **Associating File Types on Windows:** On Windows systems, the book covers how to associate Ruby scripts with the Ruby interpreter so that they can be executed directly without needing to specify the interpreter each time. #### Core Language Features - **Reserved Words:** These are keywords in Ruby that have special meanings and cannot be used as identifiers (e.g., variable names). The book lists all the reserved words and provides examples of how they are used. - **Operators:** Ruby supports a variety of operators for performing arithmetic, comparison, logical, and bitwise operations. The book covers the syntax and usage of these operators. - **Comments:** The book explains the syntax for adding comments in Ruby code, which helps in documenting and explaining the purpose of the code. - **Numbers:** Ruby has built-in support for integer and floating-point numbers. The book discusses the syntax for representing these numbers and common arithmetic operations. - **Variables:** Variables are fundamental constructs in Ruby used to store values. The book covers different types of variables, including local, instance, class, and global variables, along with constants and parallel assignment. - **Symbols:** Symbols are immutable string-like objects that are more efficient than strings for certain use cases. The book explains the syntax for creating symbols and their typical uses. #### Predefined Variables and Constants - **Predefined Variables:** Ruby defines several predefined variables that hold important values, such as `$0` for the name of the current program, `$!` for the last error message, etc. The book lists these variables and explains their purposes. - **Pseudovariables:** Pseudovariables, like `self`, `super`, and `__FILE__`, are special variables with specific behaviors and usages. The book covers their definitions and common uses. - **Global Constants:** Constants are used to define fixed values that should not change during the execution of a program. The book lists some of the global constants defined in Ruby and explains their usage. #### Conditional Statements and Method Use - **Conditional Statements:** Ruby provides constructs like `if`, `unless`, and `case` for making decisions based on conditions. The book explains the syntax and usage of these statements. - **Method Use:** Methods are central to Ruby's object-oriented nature. The book covers the syntax for defining and calling methods, including default and variable arguments. - **Classes and Modules (Mixins):** Classes and modules are used to organize code and define behavior. The book explains the syntax for defining classes and modules and the concept of mixins for reusing code. - **Lists of Methods:** The book provides comprehensive lists of methods available in the Object, String, Array, and Hash classes and the Kernel module. These lists are invaluable for understanding the capabilities of these core Ruby constructs. #### Advanced Topics - **`sprintf` and Time Formatting Directories:** Ruby provides powerful string formatting and date/time handling capabilities. The book covers the syntax and usage of `sprintf` and the time formatting options. - **Interactive Ruby (irb) and the Ruby Debugger:** irb is an interactive shell for experimenting with Ruby code. The book introduces irb and the Ruby debugger, explaining how to use them effectively. - **Ruby Documentation:** Ruby has extensive documentation, and the book provides guidance on accessing and using it to explore the language further. - **RubyGems and Rake:** The book also includes information on RubyGems, a package management system for Ruby, and Rake, a build tool similar to make. In summary, "Ruby Pocket Reference" is an indispensable resource for Ruby developers looking for a compact, easy-to-carry guide that covers the essential aspects of the language. Whether you need a refresher on basic syntax or a deeper dive into advanced topics, this book is an excellent choice.