Ruby 1.9 changes, cherry picked

以下文件只有在编辑模式下猜可以正常显示

Some of the most important improvements in ruby 1.9

• Much better threading – performance and tools are superior to ruby 1.8. Read more about threads and fibers atPaul Barry’s blog.
• Unicode support, finally. Also a brand new encoding engine has been added. There’s a very informative blog post about this onYehuda Katz’s blog.
• The interpreter’s performance had been vastly improved. Check out the (v1.9.0)benchmark.
• Rubygems is now integrated into ‘ruby’ itself.

Let’s look at the main incompatibilites that can break your code

• The shiny new String class.
• Literal Hash constructor has changed.
  • {“a”, “b”} no longer makes a Hash but a nice syntax error. You have to use {“a” => “b”} or {:a => “b”} or {a: “b”}

Now for the other important changes and upgrades

Changes in the Hash class

• Hash finally preserves insertion order
  • Ruby 1.8
    
    ^?View Code RUBY

    hash = {:a=> 'A', :b=>'B', :c=>'C', :d=>'D'}
    hash.keys ====>  [:b, :c, :d, :a]
    hash.values ====> ["B", "C", "D", "A"]

  • Ruby 1.9
    
    ^?View Code RUBY

    hash = {:a=> 'A', :b=>'B', :c=>'C', :d=>'D'}
    hash.keys ====>  [:a, :b, :c, :d]
    hash.values ====> ["A", "B", "C", "D"]

• Hash#to_s behaves much nicer
  • Ruby 1.8
    
    ^?View Code RUBY

    hash = {:a=> 1, :b=>2, :c=>3, :d=>4}
    hash.to_s ====> "b2c3d4a1"

  • Ruby 1.9
    
    ^?View Code RUBY

    hash = {:a=> 1, :b=>2, :c=>3, :d=>4}
    hash.to_s ====> "{:a=>1, :b=>2, :c=>3, :d=>4}"

• Hash#select now returns a hash, not an array
  • Ruby 1.8
    
    ^?View Code RUBY

    hash = {:a=> 1, :b=>2, :c=>3, :d=>4}
    hash.select{|k,v| k == :c }  ====> [[:c, 3]]

  • Ruby 1.9
    
    ^?View Code RUBY

    hash = {:a=> 1, :b=>2, :c=>3, :d=>4}
    hash.select{|k,v| k == :c } ====> {:c=>3}

String changes

• Single character strings
  • Ruby 1.8
    
    ^?View Code RUBY

    irb(main):001:0> ?c
    => 99	    
    irb(main):001:0> "cat"[1]
    => 97

  • Ruby 1.9
    
    ^?View Code RUBY

    irb(main):001:0> ?c
    => "c"
    irb(main):001:0> "cat"[1]
    => "a"

• Encoding, encoding, encoding
  • All strings have an additional chunk of info attached: Encoding
    
    ^?View Code RUBY

    ruby-1.9.2-p136 :003 > "whatever".encoding
     => #<Encoding:UTF-8> 
    ruby-1.9.2-p136 :004 > "whatever".encoding.name
     => "UTF-8"

  • String#size takes encoding into account – returns the encoded character count
    
    ^?View Code RUBY

    puts utf8_string.size    # >> 6
    puts latin1_string.size  # >> 6

  • You can get the raw datasize
    
    ^?View Code RUBY

    puts utf8_string.bytesize    # >> 8
    puts latin1_string.bytesize  # >> 6

  • Indexed access is by encoded data – characters, not bytes
    
    ^?View Code RUBY

    puts utf8_string[2..4]    # >> sum
    puts latin1_string[2..4]  # >> sum

  • You can change encoding by force but it doesn’t convert the data
    
    ^?View Code RUBY

    my_string = "Whatever"
    puts my_string.encoding.name  # >> US-ASCII
    my_string.force_encoding("UTF-8")
    puts my_string.encoding.name  # >> UTF-8
    
    # changing the encoding doesn't convert the data though!
    latin1_string.force_encoding("UTF-8")
    puts latin1_string.encoding.name    # >> UTF-8
    puts latin1_string.bytesize         # >> 6
    puts latin1_string.valid_encoding?  # >> false
    latin1_string =~ /AR/  # !> ArgumentError: invalid byte sequence in UTF-8

  • You can re-encode a string to ‘fix’ the above ‘error’
    
    ^?View Code RUBY

    transcoded_utf8_string= latin1_string.encode("UTF-8")
    puts transcoded_utf8_string.valid_encoding?  # >> true

  • Iterators have changed as String is not Enumerable anymore
    
    ^?View Code RUBY

    #Use each_byte, each_char or each_codepoint
    
    utf8_resume.each_byte do |byte|
      puts byte
    end
    # >> 82
    # >> 195
    # >> 169
    # >> 115
    # >> 117
    # >> 109
    # >> 195
    # >> 169
    
    utf8_resume.each_char do |char|
      puts char
    end
    # >> R
    # >> é
    # >> s
    # >> u
    # >> m
    # >> é
    
    utf8_resume.each_codepoint do |codepoint|
      puts codepoint
    end
    # >> 82
    # >> 233
    # >> 115
    # >> 117
    # >> 109
    # >> 233
    
    # if you need custom processing, you can get the enumerators with bytes, chars, lines and codepoints
    
    p utf8_resume.bytes.first(3)
    # >> [82, 195, 169]
    p utf8_resume.chars.find { |char| char.bytesize > 1 }
    # >> "é"
    p utf8_resume.codepoints.to_a
    # >> [82, 233, 115, 117, 109, 233]
    p utf8_resume.lines.map { |line| line.reverse }
    # >> ["émuséR"]

Block variables now shadow local variables

^?View Code RUBY

#Ruby 1.9

irb(main):001:0> i=0; [1,2,3].each {|i|}; i
=> 0
irb(main):002:0> i=0; for i in [1,2,3]; end; i
=> 3

#Ruby 1.8.6

irb(main):001:0> i=0; [1,2,3].each {|i|}; i
=> 3

tr and Regexp are Unicode-compatible

You can now specify source file encoding

Basic

# coding: utf-8
Emacs

# -*- encoding: utf-8 -*-
Shebang

#!/usr/local/rubybook/bin/ruby
# encoding: utf-8

Inject methods

^?View Code RUBY

#Ruby 1.9

[1,2].inject(:+)

#Ruby 1.8.6

[1,2].inject {|a,b| a+b}

Lambda shorthand syntax

^?View Code RUBY

#Ruby 1.9

p = -> a,b,c {a+b+c}
puts p.(1,2,3)
puts p[1,2,3]

#Ruby 1.8.6

p = lambda {|a,b,c| a+b+c}
puts p.call(1,2,3)

Complex numbers

^?View Code RUBY

#Ruby 1.9

Complex(3,4) == 3 + 4.im

Multi-splat

^?View Code RUBY

# This will work on both Ruby 1.8 and 1.9
a, b, c = *[1, 2], 3

# This will fail on 1.8, but work on 1.9
a, b, c = 1, *[2, 3]

# Even this will work on 1.9, but not 1.8
a, b, c, d, e, f = *[1, 2], 3, *[4, 5]

Blocks now can accept block arguments

^?View Code RUBY

define_method(:answer) { |&b| b.call(42) }