The document discusses the String#gsub method in Ruby, which performs global substitutions on a string. gsub can replace all instances of a pattern with a replacement string or run a block for each match. The pattern can be a string or regular expression. Examples show using gsub to replace numbers with strings or other numbers, and to perform operations on each digit match by passing a block.

1. gsub
M e t h o d o f t h e M o n t h
Kevin Munc
@muncman

2. Global SUBstitutions
String#gsub(pattern, replacement)
String#gsub(pattern) { |match| block }

3. Global SUBstitutions
String#gsub(pattern, replacement)
String#gsub(pattern) { |match| block }
The ‘pattern’ can be a String or a Regexp.

4. seq = "0123456789"
=> "0123456789"
seq.gsub('no match',
'anything')
=> "0123456789"
seq.gsub('567', '___')
=> "01234___89"

5. seq.gsub('567', '_')
=> "01234_89"
seq.gsub('567', '.....')
=> "01234.....89"
seq.gsub('567','')
=> "0123489"

7. seq.gsub(/[5-9]/, 'g')
=> "01234ggggg"

8. seq.gsub(/[5-9]/, 'g')
=> "01234ggggg"
seq.sub(/[5-9]/, 'g')
=> "01234g6789"

9. Bang!
(like a gun shot in a
ghetto)
seq = "Matz Dave DHH Zed Why"
=> "Matz Dave DHH Zed Why"

10. Bang!
(like a gun shot in a
ghetto)
seq = "Matz Dave DHH Zed Why"
=> "Matz Dave DHH Zed Why"
seq.gsub!('Zed ','')
=> "Matz Dave DHH Why"
seq
=> "Matz Dave DHH Why"

11. With Blocks

12. With Blocks
“0123456789”.gsub(/d/) do |digit|
digit.to_i + 1
end
=> "12345678910"

13. With Blocks
“0123456789”.gsub(/d/) do |digit|
digit.to_i + 1
end
=> "12345678910"
“0123456789”.gsub(/d/) do |digit|
digit.to_i * 2
end
=> "024681012141618"

14. seq = "0123456789"
=> "0123456789"

15. seq = "0123456789"
=> "0123456789"
seq.gsub(/d/) do |digit|
(digit.to_i * 2).to_s + '-'
end
=> "0-2-4-6-8-10-12-14-16-18-"

16. seq = "0123456789"
=> "0123456789"

17. seq = "0123456789"
=> "0123456789"
seq.gsub(/d/) { |digit|
digit if (digit.to_i % 2 == 0)
}
=> "02468"

18. "COJUG".gsub(/[^C].*$/, 'RB')
=> "CRB"

20. "a1b2c3".gsub(/d/) do |x|
puts "#{x} cheers for CRB!"
end
1 cheers for CRB!
2 cheers for CRB!
3 cheers for CRB!
=> "abc"

21. Questions? Answers? Hungry?
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