Learn Ruby 2011 - Session 3
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This document covers foundational Ruby programming concepts, including arrays, hashes, symbols, control structures, regular expressions, blocks, and iterators. It provides examples and encourages readers to practice by completing exercises and working on Ruby koans. The document also outlines reading assignments for beginners and users seeking a deeper understanding of classes and variables in Ruby.
![Arrays
array = [“One”,”Two”,”Three”]
puts array[0]
One
array.each { |v| puts v }
One
Two
Three](https://image.slidesharecdn.com/session03-110211122337-phpapp02/85/Learn-Ruby-2011-Session-3-6-320.jpg)
![Hashes
hash = {‘one’ => “One”, :two => ”Two”}
puts hash[‘one’]
One
puts hash[:two]
Three](https://image.slidesharecdn.com/session03-110211122337-phpapp02/85/Learn-Ruby-2011-Session-3-8-320.jpg)
![Control Structures
for i in 1..3
# ...
end
for i in [‘one’,‘two’,‘three’]
# ...
end](https://image.slidesharecdn.com/session03-110211122337-phpapp02/85/Learn-Ruby-2011-Session-3-19-320.jpg)
![Iterators
[‘One’,‘Two’,‘Three’].each do |val|
puts val
end
One
Two
Three](https://image.slidesharecdn.com/session03-110211122337-phpapp02/85/Learn-Ruby-2011-Session-3-24-320.jpg)
Learn Ruby 2011 - Session 3
- 1. Learn Ruby 2011 Session 3
- 2. Our Sponsors Flatsourcing, iSeatz, Koda, and Launchpad
- 3. Language Crashing Learning the basics in pieces
- 4. Questions Having any problems? Discover anything cool?
- 5. Arrays • An Array is an ordered list of values • Arrays in Ruby are zero-indexed
- 6. Arrays array = [“One”,”Two”,”Three”] puts array[0] One array.each { |v| puts v } One Two Three
- 7. Hashes • Hashes are unordered lists of values • Hashes are indexed using “keys” which can being either strings or symbols
- 8. Hashes hash = {‘one’ => “One”, :two => ”Two”} puts hash[‘one’] One puts hash[:two] Three
- 9. Symbols • Symbols are essentially constants that don’t need to be declared ahead of time • A Symbol has a simple string-like representation and is guaranteed to have a unique value
- 10. Symbols def walk(direction) if direction == :north # ... end end
- 11. Symbols • Symbols are most commonly found as the keys for hashes • They are slightly more memory efficient than using strings for the same purposes
- 12. Control Structures • Control structures allow you to handle conditional behaviors • Control structures allow you to handle iterations/loops
- 13. Control Structures • if ... else ... elsif • while • case ... when • for ... in • until • unless
- 14. Control Structures if i == 3 # ... elsif i == 4 # ... else # ... end
- 15. Control Structures unless i == 3 # ... end
- 16. Control Structures while i < 3 # ... end
- 17. Control Structures until i < 3 # ... end
- 18. Control Structures case i when 3 # ... when 4 # ... else # ... end
- 19. Control Structures for i in 1..3 # ... end for i in [‘one’,‘two’,‘three’] # ... end
- 20. Regular Expressions • Regular Expressions are used for text parsing and manipulation • They can represent a sort of programming language unto themselves
- 21. Blocks • Sections of code that can be passed to methods like parameters • Represented as code within curly braces or between do and end
- 22. Blocks def call_block puts "Start of method" yield puts "End of method" end call_block { puts "In the block" } Start of method In the block End of method
- 23. Iterators • A type of code block that works with successive values of some collection • Used extensively for arrays and hashes
- 24. Iterators [‘One’,‘Two’,‘Three’].each do |val| puts val end One Two Three
- 25. Reviewing • Arrays & Hashes • Symbols • Control Structures • Regular Expressions • Blocks & Iterators
- 26. For Next Week For the New to Programming • Read Chapters 5, 6, 7 & 8 in LtP • Complete exercises for each chapter For Everyone • Read Chapter 2, 7 & 9 in PR1.9 • Work on the Ruby Koans at a leisurely pace
- 27. Next Week • Deeper into Classes & Variables
- 28. Exercises • Visit http://rubykoans.com/ & Download • Begin working through the Koans by running `ruby path_to_enlightenment.rb` •