Ruby Code Snippet

sfatsdu · 发表于 2005-8-8 18:52:43

关于上面的帖子再多说几句,最令人奇怪的是当你创建了某个类的实例,即

f = Foo.new

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你可以继续再f上重新定义各种各样的method,上面已经有了例子我就不说了,看的比较清楚的办法是像这样

class << f
def inst_meth
xxx
xxx
end
end

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瞧,我们再f 这个实例上又打开了一个类,这里定义的方法可以overide原先class Foo中的行为.Matz称之为singleton class notation.其他的叫法有metaclass或者eigenclass,不一而足

sfatsdu · 发表于 2005-8-11 14:56:44

看看open-uri模块的威力，相当于curl,和Ruby的IO体系很好的融合在一起
另一个有意思的地方是"00001".upto("00050")
来自
http://redhanded.hobix.com

#!/usr/bin/ruby
require 'open-uri'
BASE_URL = "http://www.rubyist.net/~matz/slides/oscon2005/mgp"
"00001".upto("00059") do |n|
puts "Fetching #{n}.html... ..."
File.open(n + ".html", "w") do |f|
f.write(open(BASE_URL + n + ".html").read)
end
end

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sfatsdu · 发表于 2005-8-16 16:03:03

meta-programming...

class Foo
class << self
def class_meth; xxx; end
end
def inst_meth; xxx; end
end

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As pointed out before, we use the notation of
class << self; def xxx; end; end
is the same as
def self.xxx; end
but use this notation makes that class methods look more consistant with class instance methods, and improve the readbility of your code

sfatsdu · 发表于 2005-8-19 11:02:48

I collected some good article from college bbs, save them as html file, they look like this
<html>
<pre>
original post
</pre>
</html>
The following script extract original post from html files, save them as filename.txt
Here I use this ruby library htmltokenizer, ported from Perl
http://rubyforge.org/projects/htmltokenizer/

require 'html/htmltokenizer'
collection = Dir['*.html'] # collect inserested html file names in a array...
collection.each do |t| # do our magic in blocks
token = HTMLTokenizer.new(IO.read(t))
token.getTag("pre")
File.open(File::basename(t, ".html") + ".txt", 'w') do |handle| # nested block
handle << token.getText("/pre")
end
end

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sfatsdu · 发表于 2005-8-20 10:31:06

meta-programming

class Foo
attr_reader :instance_variable
class << self
def initialize(str)
@instance_variable = str
end
end
end
foo = Foo::new("hehe")
foo.instance_variable # => "hehe"

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so we call the method access_reader(xxx) in the definition of class, and we get the instance method "xxx", we don't use the normal way of

def instance_variable
@instance_variable
end

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you may think this is just a short notation of making methods, of course it is, however, you may extensively use this technique in your programming practice. The first good practice is define your own version of attr, attr_reader, attr_writer, attr_accessor methods. Why? since then, our class instance can interactive with other objects, that will simplify many things.

sfatsdu · 发表于 2005-8-22 14:37:19

module Enumerable
def paginate(size)
i = 0
self.inject([]) {|arr, item|
(arr[i/size] ||= []) << item
i += 1
arr
}
end
end
__END__
(1..14).to_a.paginate(4) # => [[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14]]

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sfatsdu · 发表于 2005-8-22 21:50:45

想象上面那个例子用在论坛或者组织照片，文档的网络应用上...
这里也反映了Ruby的一个特点：Class都是Open的，完全可以根据程序流程的需要，扩展原有的Class，甚至是针对每个instance作扩展...

sfatsdu · 发表于 2005-8-23 15:14:27

请Python大虾们举几个generator作为iterator的例子，谢谢了

sfatsdu · 发表于 2005-9-10 00:25:59

def Hash::[]( enum )
enum.inject({}) do |hsh, (k,v)|
hsh[k] = v
hsh
end
end
__END__
keys = %w(a b c) # keys = ['a', 'b', 'c']
values = [1,2,3] # values = [1, 2, 3]
Hash[keys.zip(values)] # {"a"=>1, "b"=>2, "c"=>3}

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sfatsdu · 发表于 2006-2-18 12:59:21

好久没有看Ruby了，一个新的例子
首先做一个modle，批量定义了 <,=,>三个method，ri define_method可以看到详细说明

module A
["<", "=",">"].each do |op|
define_method(op) {|comparision|
eval "#{self.order} #{op} #{comparision.order}"}
end
end

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一个简单的class

class B
attr_accessor :order
def initialize(order)
@order = order
end
end
a = B::new(100)
b = B::new(200)

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现在呢
a.order # =>100
b.order # =>200
a < b # => NoMethodError
把B的定义改作

class B
include A ＃包含进模块A
attr_accessor :order
def initialize(order)
@order = order
end
end

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好了，对于a,b这两个类B的实例，用instance variable order来进行比较
a > b # => false

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