You are previewing Learning Ruby.

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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Date and Time

Figuring out the day and time is important in daily life and in computing, so Ruby naturally offers facilities to do so. In this section, I'll talk about Ruby's Date and Time classes.

The Time Class

I cover many of the most commonly used Time methods here. See http://ruby-doc.org/core/classes/Time.html for documentation on all the Time methods.

To determine the current time, use the now method (or its synonym new) from Time. Calling the method twice can help you determine how much time has elapsed in between.

start = Time.now # => Tue Jan 30 04:12:50 -0700 2007
stop = Time.now # => Tue Jan 30 04:13:00 -0700 2007

To set a given time, use the local method (mktime is a synonym):

local_time = Time.local( 2007, "jan", 30, 1, 15, 20 )
# => Tue Jan 30 01:15:20 -0700 2007

The arguments to this call to local are (in order) year, month, date, hour, minutes, seconds. You can also call local with these arguments:

my_time = Time.local( 20, 15, 1, 30, "jan", 2007, 2, 30, false, "MST")
# => Tue Jan 30 01:15:20 -0700 2007

In this call, the arguments, in order, are seconds, minutes, hour, day, month, year, day of the week, day of the year, is-it-daylight-savings-time?, and timezone.

From a Time object you can get all kinds of particulars, such as the day, the day of the week, and the day of the year:

stop.day # the day of the month => 30
stop.yday # how many days so far this year => 30
stop.wday # the day of the week => 2, or Tue (Sun == 0)

You can retrieve the year, the month, and the timezone: ...

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