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Learning Ruby

Cover of Learning Ruby by Michael Fitzgerald Published by O'Reilly Media, Inc.
  1. Learning Ruby
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. A Note Regarding Supplemental Files
    3. Preface
      1. Who Should Read This Book?
      2. How This Book Works
      3. About the Examples
      4. How This Book Is Organized
      5. Conventions Used in This Book
      6. Comments and Questions
      7. Safari® Enabled
      8. Acknowledgments
    4. 1. Ruby Basics
      1. Hello, Matz
      2. Interactive Ruby
      3. Resources
      4. Installing Ruby
      5. Permission Denied
      6. Associating File Types on Windows
      7. Review Questions
    5. 2. A Quick Tour of Ruby
      1. Ruby Is Object-Oriented
      2. Ruby's Reserved Words
      3. Comments
      4. Variables
      5. Strings
      6. Numbers and Operators
      7. Conditional Statements
      8. Arrays and Hashes
      9. Methods
      10. Blocks
      11. Symbols
      12. Exception Handling
      13. Ruby Documentation
      14. Review Questions
    6. 3. Conditional Love
      1. The if Statement
      2. The case Statement
      3. The while Loop
      4. The loop Method
      5. The for loop
      6. Execution Before or After a Program
      7. Review Questions
    7. 4. Strings
      1. Creating Strings
      2. Concatenating Strings
      3. Accessing Strings
      4. Comparing Strings
      5. Manipulating Strings
      6. Case Conversion
      7. Managing Whitespace, etc.
      8. Incrementing Strings
      9. Converting Strings
      10. Regular Expressions
      11. 1.9 and Beyond
      12. Review Questions
    8. 5. Math
      1. Class Hierarchy and Included Modules
      2. Converting Numbers
      3. Basic Math Operations
      4. Ranges
      5. Inquiring About Numbers
      6. More Math Methods
      7. Math Functions
      8. Rational Numbers
      9. Prime Numbers
      10. Review Questions
    9. 6. Arrays
      1. Creating Arrays
      2. Accessing Elements
      3. Concatenation
      4. Set Operations
      5. Unique Elements
      6. Blow Your Stack
      7. Comparing Arrays
      8. Changing Elements
      9. Deleting Elements
      10. Arrays and Blocks
      11. Sorting Things and About Face
      12. Multidimensional Arrays
      13. 1.9 and Beyond
      14. Other Array Methods
      15. Review Questions
    10. 7. Hashes
      1. Creating Hashes
      2. Accessing Hashes
      3. Iterating over Hashes
      4. Changing Hashes
      5. Converting Hashes to Other Classes
      6. 1.9 and Beyond
      7. Other Hash Methods
      8. Review Questions
    11. 8. Working with Files
      1. Directories
      2. Creating a New File
      3. Opening an Existing File
      4. Deleting and Renaming Files
      5. File Inquiries
      6. Changing File Modes and Owner
      7. The IO Class
      8. Review Questions
    12. 9. Classes
      1. Defining the Class
      2. Instance Variables
      3. Accessors
      4. Class Variables
      5. Class Methods
      6. Inheritance
      7. Modules
      8. public, private, or protected
      9. Review Questions
    13. 10. More Fun with Ruby
      1. Formatting Output with sprintf
      2. Processing XML
      3. Date and Time
      4. Reflection
      5. Using Tk
      6. Metaprogramming
      7. RubyGems
      8. Exception Handling
      9. Creating Documentation with RDoc
      10. Embedded Ruby
      11. Review Questions
    14. 11. A Short Guide to Ruby on Rails
      1. Where Did Rails Come From
      2. Why Rails?
      3. What Have Other Folks Done with Rails?
      4. Hosting Rails
      5. Installing Rails
      6. Learning Rails
      7. A Brief Tutorial
      8. Review Questions
    15. A. Ruby Reference
      1. Ruby Interpreter
      2. Ruby's Reserved Words
      3. Operators
      4. Escape Characters
      5. Predefined Variables
      6. Global Constants
      7. Regular Expressions
      8. String Unpack Directives
      9. Array Pack Directives
      10. Sprintf Flags and Field Types
      11. File Tests
      12. Time Formatting Directives
      13. RDoc Options
      14. Rake
    16. B. Answers to Review Questions
      1. Chapter 1 Review Questions
      2. Chapter 2 Review Questions
      3. Chapter 3 Review Questions
      4. Chapter 4 Review Questions
      5. Chapter 5 Review Questions
      6. Chapter 6 Review Questions
      7. Chapter 7 Review Questions
      8. Chapter 8 Review Questions
      9. Chapter 9 Review Questions
      10. Chapter 10 Review Questions
      11. Chapter 11 Review Questions
    17. Glossary
    18. Index
    19. About the Author
    20. Colophon
    21. SPECIAL OFFER: Upgrade this ebook with O’Reilly
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Chapter 10. More Fun with Ruby

It's time to explore beyond the basics and move into some other areas of Ruby. Here you'll learn how to use the sprintf method to format output, process or generate XML with REXML or XML Builder, use reflection methods, use RubyGems, create documentation with RDoc, and do some error handling. You'll even do a little metaprogramming and embedded Ruby (ERB). The purpose of this chapter is to expand your knowledge and broaden your experience before cutting you loose. After this, only Chapter 11 remains.

Formatting Output with sprintf

The Kernel module has a method called sprintf (which also has a synonym called format) for creating formatted strings. If you have C programming in your DNA, as many programmers do, it is likely that you will want to reach for sprintf to do all kinds of string formatting chores for you. sprintf relies on a format string—which includes format specifiers, each preceded by a %—to tell it how to format a string. For example, let's say you wanted to print out the number 237 in binary format. Enter this:

sprintf( "%b", 237 ) # => "11101101"

The format specifier %b indicates that you want a binary result. b is the field type for binary, and the argument 237 is the number you want to convert to binary, which sprintf does very handsomely. sprintf doesn't actually print the return value to standard output (the screen); to do that you would have to use printf, another Kernel method:

printf( "%b", 237 ) # => 11101101

which is nearly identical ...

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