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Conditions and loops

if / elsif / unless, case, iterating with each and times, while, and next / break.

Runs in Zerethon IDE · Ruby 4.0 Official Ruby documentation ↗
main.rb 
(1..5).each do |n|
  if n.even?
    puts "#{n} even"
  elsif n == 5
    puts "#{n} last"
  else
    puts "#{n} odd"
  end
end

i = 3
while i > 0
  i -= 1
  next if i == 1
  puts "i = #{i}"
end

%w[apple pear].each_with_index { |fruit, index| puts "#{index} #{fruit}" }

day = 6
kind = case day
       when 0, 6 then "weekend"
       when 1..5 then "weekday"
       end
puts kind

temperature = -2
puts "freezing" unless temperature > 0
puts 3.times.to_a.inspect

Output

1 odd
2 even
3 odd
4 even
5 last
i = 2
i = 0
0 apple
1 pear
weekend
freezing
[0, 1, 2]
  • 1..5 includes 5; 1...5 stops before it.
  • Every if, while, do and def block ends with end.
  • puts x if condition and next if condition are one-line modifiers.
  • Ruby code rarely uses for; each, times, upto and each_with_index are the usual loops.

Related topics

Official references