#1: INTERPOLATE, NOT CONCATENATE #2: AVOID DOUBLE NEGATIVES #3: ARRAY.INJECT #4: CHAIN ARRAY METHODS #5: ZERO DIVISION ERROR

1. 5 RANDOM RUBYTIPS
Saigon.rb Ruby Meetup
By StevenYap
6th Oct 2015

2. StevenYap
stevenyap@futureworkz.com
https://github.com/stevenyap

8. • Host Saigon.rb Ruby Meetup
• Founder of Futureworkz
• Ruby on Rails coder
• Agile startup consultant
• Pretends to be extrovert
• Introvert by nature

9. Awesome Ruby on Rails Applications for Startups
http://www.futureworkz.com
https://github.com/futureworkz/playbook

10. 5 RANDOM RUBYTIPS

11. #1: INTERPOLATE, NOT
CONCATENATE
# concatenate
puts “error description” + e.cause.to_s + “happened on: ” + Time.now.to_s

12. #1: INTERPOLATE, NOT
CONCATENATE
# interpolate
puts "error description #{e.cause} happened on: #{Time.now}"

13. #1: INTERPOLATE, NOT
CONCATENATE
# interpolate
puts "error description #{e.cause} happened on: #{Time.now}”
# concatenate
puts “error description” + e.cause.to_s + “happened on: ” + Time.now.to_s

14. #1: INTERPOLATE, NOT
CONCATENATE
• Easier to read
• Automatic #to_s
• Type less

15. #2:AVOID DOUBLE
NEGATIVES
# Double negatives
unless !post.published?
# do something
end

16. #2:AVOID DOUBLE
NEGATIVES
# Be positive!
if post.published?
# do something
end

17. #2:AVOID DOUBLE
NEGATIVES
# Be positive!
if post.published?
# do something
end
# Double negatives
unless !post.published?
# do something
end

18. #2:AVOID DOUBLE
NEGATIVES
• Much easier to read
• Makes you think more positively
• Makes you happier (like Ruby)

19. #3:ARRAY.INJECT
# Sum up all numbers in an array
array = [1,2,3,4,5]
sum = 0
array.each do |number|
sum += number
end
return sum # => 15

20. #3:ARRAY.INJECT
# Sum up all numbers in an array
array = [1,2,3,4,5]
array.inject(0) { |sum, number| sum + number } # => 15

21. #3:ARRAY.INJECT
# Sum up all numbers in an array
array = [1,2,3,4,5]
array.inject(0) { |sum, number| sum + number } # => 15
# Sum up all numbers in an array
array = [1,2,3,4,5]
sum = 0
array.each do |number|
sum += number
end
return sum # => 15

22. #3:ARRAY.INJECT
• Easier to read (once you get used to it!)
• Shorter code
• Common Ruby idiom

23. #4: CHAIN ARRAY METHODS
# Given an array, return a new array with
# Only even numbers
# The numbers are multiplied by 3
# Reject all numbers that are greater than 20
array =[1,2,3,4,5,6,7,8,9,10]
result = []
array.each do |x|
if x % 2 == 0
result << x * 3 if x * 3 < 21
end
end
return result # => [6, 12, 18]

24. #4: CHAIN ARRAY METHODS
# Given an array, return a new array with
# Only even numbers
# The numbers are multiplied by 3
# Reject all numbers that are greater than 20
array =[1,2,3,4,5,6,7,8,9,10]
array.select { |x| x % 2 == 0 }.map { |x| x * 3}.reject { |x| x > 20}
# => [6, 12, 18]

25. #4: CHAIN ARRAY METHODS
• More expressive
• Shorter code
• Common Ruby idiom

26. #5: ZERO DIVISION ERROR
1/0
# ZeroDivisionError: divided by 0

27. #5: ZERO DIVISION ERROR
1/0.0 # => Infinity

29. #5: ZERO DIVISION ERROR
• No idea how it can be helpful to you
• But it is fun to know
• Makes you happier (like Ruby!)

30. THANKYOU