What's New in Ruby 2.4

Talk given to the Dallas Ruby Brigade on Tuesday, February 7.

Transcript

1. Ruby 2.4
2. binding.irb • Quick way to explore environment at a point • Uses the mysterious Kernel#binding object (Binding) • Changes you make persist back to program binding.rb
3. Unified Integers - Fixnum and Bignum are now Integer # Before Ruby 2.4 1.class #=> Fixnum (2 ** 62).class #=> Bignum # Ruby 2.4 1.class #=> Integer (2 ** 62).class #=> Integer
4. Unified Integers - Fixnum and Bignum are now Integer • Fixnum and Bignum are deprecated in 2.4 • Writing a gem that might have to deal with both? – Check 1.class – Pre-2.4, you will get Fixnum – 2.4, you will get Integer
5. New Integer#digits method Want to operate over the digits of an integer? Pre-2.4 123.to_s.chars.map(&:to_i).reverse # => [3, 2, 1] 2.4 123.digits # => [3, 2, 1] 123.digits.reverse # => [1, 2, 3]
6. Precision for float modifiers
7. Precision for float modifiers PI = 3.141592653589793 Pre-2.4 PI.floor # => 3 (Fixnum) 2.4 PI.floor # => 3 (Integer) PI.floor(5) # => 3.14159 Applies to ceil, floor, truncate, round (always applied to round)
8. Precision for float modifiers NUM = 123456789 NUM.round(3) # => 123456789.0 (Float) NUM.round(-3) # => 123457000 (Integer) NUM = 12345.6789 NUM.round(-2) # => 12300 (Integer) NUM.round(0) # => 12346 (Integer) NUM.round(-10) # => 0 (Integer)
9. Float#round options PI = 3.1415 PI.round(3, half: :up) => 3.142 PI.round(3, half: :down) => 3.141 PI.round(3, half: :even) => 3.142
10. Specify string buffer size String.new('foo', capacity: 1000)
11. Symbol#match now works like String#match # 2.3 :hello_ruby.match(/ruby/) #=> 6 # 2.4 :hello_ruby.match(/ruby/) #=> #<MatchData "ruby"> 'hello_ruby'.match(/ruby/) #=> #<MatchData "ruby">
12. IO#gets and other methods get a chomp flag So you want to remove newline characters from your input? # In 2.3, you did this foo = gets.chomp # 2.4 foo = gets(chomp: true) Works for #gets, #readline, #each_line, #readlines and IO.foreach.
13. Regexp#named_captures pattern = /(?<first_name>John) (?<last_name>\w+)/ pattern.named_captures => {"first_name"=>[1], "last_name"=>[2]} pattern.match('John Brown') => #<MatchData "John Brown" first_name:"John"last_name:"Brown"> New in 2.4 captures = pattern.match('John Brown').named_captures => {"first_name"=>"John", "last_name"=>"Brown"} captures['first_name'] => "John” captures.values_at(:last_name) => ‘Brown’
14. Enumerable#sum [1, 1, 2, 3, 5, 8, 13, 21].sum # => 54 • Starts with an implied (integer) zero • You can provide a starting parameter [1, 1, 2, 3, 5, 8, 13, 21].sum(100) # => 154
15. Enumerable#sum You can sum anything with method ‘+’ defined… 'Steve' + 'Crozier' => "SteveCrozier” ['Steve', 'Crozier'].sum => TypeError: String can't be coerced into Integer …but you must provide a starting value, if not an Integer ['Steve', 'Crozier'].sum('') => "SteveCrozier"
16. #empty? method was added to Dir, File and Pathname Dir.empty?('path/to/some/dir') File.empty?('path/to/some/file') # => same as File.zero? Pathname.new('file-or-dir').empty?
17. Regexp#match? This new method returns true or false without updating the $~ global variable. Since it doesn’t create a MatchData object or update $~, it performs better than #match. /Steve/.match(‘Steve’) # => slower /Steve/.match?(‘Steve’) # => faster
18. Quiz Time SMS: Text stevecrozier574 to 22333 or Web: pollev.com/stevecrozier574