Eloquen - Chapter 2 - use right control
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This document discusses control flow in Ruby including conditionals like if/unless/while/until, case statements, and handling false values. The key points are: - If/unless and while/until can be used for conditional execution based on true/false values - Case statements allow executing different code blocks based on matches - Each should be used instead of for to iterate over arrays - Only nil and false are treated as false values in Ruby
Eloquen - Chapter 2 - use right control
- 1. Chapter 2 Choose The Right Control There are 4 point: • If, Unless, While & Until • Use each, not for • Case Logic • False Value
- 2. 1. If, Unless, While & Until if & unless: Usage: if condition unless condition do_something do_something end end # do_something # do_something when condition is true. when condition is false.
- 3. 1. If, Unless, While & Until if & unless without else statement: Code: one line statement “eat something” If hungry? “stop eating” unless hungry? “stop eating” if full? **Not: “stop eating” if !hungry?
- 4. 1. If, Unless, While & Until if & unless with else statement: Code: If hungry? If full? “eat something” “stop eating” else else “stop eating” “eat something” end end
- 5. 1. If, Unless, While & Until if & unless with else statement: **Not: never use unless with else statement unless hungry? “stop eating” else “eat something” end
- 6. 1. If, Unless, While & Until Ternary: Usage: condition ? true : false Code: hungry? ? eat_something : stop_eating full? ? stop_eating: eat_something
- 7. 1. If, Unless, While & Until while & until: Usage: while condition until condition do_something do_something end end # loop do_something # loop do_something when condition is true. when condition is false.
- 8. 1. If, Unless, While & Until while & until: Code: one line statement eat_something while hungry? stop_eating until hungry? stop_eating while full? **Not: stop_eating while !hungry?
- 9. 2. Use each, Not for Code: **Not: array.each do |arr| for arr in array puts arr puts arr end end when use this, array.each { |arr| puts arr } ruby will call each. 2 level calling.
- 10. 3. Case Logic Code: case title when 'War And Peace' puts 'Tolstoy' when 'Romeo And Juliet' puts 'Shakespeare' else puts "Don't know" end
- 11. 3. Case Logic author = case title when 'War And Peace' then 'Tolstoy' when 'Romeo And Juliet' then 'Shakespeare' else "Don't know" end
- 12. 3. Case Logic case title when /War And .*/ puts 'Maybe Tolstoy?' when /Romeo And .*/ puts 'Maybe Shakespeare?' else puts 'Absolutely no idea...' end
- 13. 4. False Value Only nil and false are treated as false. Code: @first_name = ‘Chaung‘ unless @first_name @first_name ||= ‘Chaung’ **Note: do not use this for boolean type @boolean = false @boolean ||= true
- 14. Thank You