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最新评论
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zhangyou1010:
回去倒立去,哈哈。
作为一个程序员,身体很重要! -
Hooopo:
Ruby MetaProgramming is all abo ...
Metaprogramming Ruby -
orcl_zhang:
yiqi1943 写道LZ现在上学还是工作呢工作好多年了。不过 ...
2011年 -
yiqi1943:
LZ现在上学还是工作呢
2011年 -
tjcjc:
query cache
就是一个简单的hash
key就是sq ...
Rails sql延迟加载和自带缓存
1,先看api
2,to_proc经常和&一起使用.
可以把block传递给带block的方法.block的to_proc返回的就是本身.
如果对象自带to_proc方法的话,就可以把它当作带"&"的参数传给带block方法(默认状态下,Proc、Method对象都有to_proc方法)。方法调用时会执行to_proc,它将返回Proc对象.
3,to_proc和method_missing
4,Going crazy
可以让&使用多个参数,更性感。
What I always regretted though was not being to pass any arguments, so I hacked and monkeypatched a bit, and got:
Not that this is any shorter than just creating the darn block in the first place. But hey, it’s a good exercise in metaprogramming and show of more of Ruby’s awesome flexibility.
After this I remembered something similar that annoyed me before. It’s that Rails helper methods are just a bag of methods available to, because they are mixed in your template. So if you have an array of numbers that you want to format as currency, you’d have to do:
What if I could apply some to_proc-love to that too? All these helper methods cannot be added to strings, fixnums, and the likes; that would clutter way to much. Rather, it might by a nice idea to use procs that understands helper methods. Here is what I created:
I used a clean blank class (in Ruby 1.9, you’d want to inherit it from BasicObject), in which I will provide the proper proc-object. I play around with the argument list a bit, handling multiple arguments and blocks too. You can now use this syntax:
That is a lot sexier if you as me. And you can use it in any object, not just inside views. And lets add some extra arguments and some Enumerator-love too:
In case you are wondering, the position you can specify is to tell where the arguments need to go. Position 0 is the method name, so you shouldn’t use that, but any other value is okay. An example might be that you cant to wrap an array of texts into span-tags:
So there you have it. I’m probably solving a problem that doesn’t exist. It is however a nice example of the awesome power of Ruby. I hope you’ve enjoyed this little demonstration of the possible uses of to_proc.
最后的一部分来自于http://iain.nl/2010/02/going-crazy-with-to_proc/
引用
Method#proc
meth.to_proc => prc
Returns a Proc object corresponding to this method.
prc.to_proc → prc
Part of the protocol for converting objects to Proc objects. Instances of class Proc simply return themselves.
meth.to_proc => prc
Returns a Proc object corresponding to this method.
prc.to_proc → prc
Part of the protocol for converting objects to Proc objects. Instances of class Proc simply return themselves.
2,to_proc经常和&一起使用.
可以把block传递给带block的方法.block的to_proc返回的就是本身.
如果对象自带to_proc方法的话,就可以把它当作带"&"的参数传给带block方法(默认状态下,Proc、Method对象都有to_proc方法)。方法调用时会执行to_proc,它将返回Proc对象.
pobj = lambda {|v| p v } [1,2,3].each(&pobj) => 1 2 3
class Foo def to_proc lambda {|v| p v} end end [1,2,3].each(&Foo.new) => 1 2 3
class Symbol def to_proc proc { |obj, *args| obj.send(self, *args) } end end projects.collect(&:name) [1, 2, 3].map(&:to_s.to_proc) #=> ["1", "2", "3"]
class Person < ActiveRecord::Base; end; [{:name => 'Dan'}, {:name => 'Josh'}].map(&Person.method(:new)) class Class def to_proc proc(&method(:new)) end end [{:name => 'Dan'}, {:name => 'Josh'}].map(&Person)
3,to_proc和method_missing
module Kernel protected def it() It.new end alias its it end class It undef_method(*(instance_methods - %w*__id__ __send__*)) def initialize @methods = [] end def method_missing(*args, &block) @methods << [args, block] unless args == [:respond_to?, :to_proc] self end def to_proc lambda do |obj| @methods.inject(obj) do |current,(args,block)| current.send(*args, &block) end end end end File.read("/etc/passwd").split.sort_by &it.split(":")[2] User.find(:all).map &its.contacts.map(&its.last_name.capitalize)
4,Going crazy
可以让&使用多个参数,更性感。
What I always regretted though was not being to pass any arguments, so I hacked and monkeypatched a bit, and got:
class Symbol def with(*args, &block) @proc_arguments = { :args => args, :block => block } self end def to_proc @proc_arguments ||= {} args = @proc_arguments[:args] || [] block = @proc_arguments[:block] @proc_arguments = nil Proc.new { |obj, *other| obj.send(self, *(other + args), &block) } end end #So you can now write: some_dates.map(&:strftime.with("%d-%M-%Y"))
Not that this is any shorter than just creating the darn block in the first place. But hey, it’s a good exercise in metaprogramming and show of more of Ruby’s awesome flexibility.
After this I remembered something similar that annoyed me before. It’s that Rails helper methods are just a bag of methods available to, because they are mixed in your template. So if you have an array of numbers that you want to format as currency, you’d have to do:
<%= @prices.map { |price| number_to_currency(price) }.to_sentence %>
What if I could apply some to_proc-love to that too? All these helper methods cannot be added to strings, fixnums, and the likes; that would clutter way to much. Rather, it might by a nice idea to use procs that understands helper methods. Here is what I created:
module ProcProxyHelper def it(position = 1) ProcProxy.new(self, position) end class ProcProxy instance_methods.each { |m| undef_method(m) unless m.to_s =~ /^__|respond_to\?|method_missing/ } def initialize(object, position = 1) @object, @position = object, position end def to_proc raise "Please specify a method to be called on the object" unless @delegation Proc.new { |*values| @object.__send__(*@delegation[:args].dup.insert(@position, *values), &@delegation[:block]) } end def method_missing(*args, &block) @delegation = { :args => args, :block => block } self end end end
I used a clean blank class (in Ruby 1.9, you’d want to inherit it from BasicObject), in which I will provide the proper proc-object. I play around with the argument list a bit, handling multiple arguments and blocks too. You can now use this syntax:
<%= @prices.map(&it.number_to_currency).to_sentence %>
That is a lot sexier if you as me. And you can use it in any object, not just inside views. And lets add some extra arguments and some Enumerator-love too:
class SomeClass include ProcProxyHelper def initialize(name, list) @name, @list = name, list end def apply(value, index, seperator) "#{@name}, #{index} #{separator} #{value}" end def applied_list @list.map.with_index(&it.apply(":")) end end
In case you are wondering, the position you can specify is to tell where the arguments need to go. Position 0 is the method name, so you shouldn’t use that, but any other value is okay. An example might be that you cant to wrap an array of texts into span-tags:
<%= some_texts.map(&it(2).content_tag(:span, :class => "foo")).to_sentence %>
So there you have it. I’m probably solving a problem that doesn’t exist. It is however a nice example of the awesome power of Ruby. I hope you’ve enjoyed this little demonstration of the possible uses of to_proc.
最后的一部分来自于http://iain.nl/2010/02/going-crazy-with-to_proc/
发表评论
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Ruby 搭建环境
2013-06-01 11:17 2051http://kidlet.sinaapp.com/blog/ ... -
ActiveRecord::Dirty
2011-11-21 10:29 785引用Track unsaved attribute chang ... -
Metaprogramming Ruby
2011-09-30 16:11 1182P30 In a sense, the class keywo ... -
RVM Install
2011-09-17 15:17 874http://beginrescueend.com/ -
json
2011-09-15 09:51 815http://flori.github.com/json/ -
Rails计算某月最后一天
2011-08-12 10:46 1426经常忘记这个函数.mark下. 引用end_of_day, e ... -
关于浮点数精度的问题
2011-05-11 15:50 1281在项目里遇到一个很诡异的问题,因为有一些浮点数的计算,总 ... -
Ruby Memoization(转载)
2010-11-28 23:45 820转载http://fuliang.iteye.com/blog ... -
included() vs extended()
2010-11-04 19:48 756# A little helper from _why cl ... -
Nesting Is Different From Inclusion
2010-10-17 10:02 791Nesting Is Different From Inclu ... -
Regular Expressions
2010-10-16 22:55 904... -
ruby里的方法作用域
2010-08-11 09:51 1093在java里private方法在Java当中的含义是只在当前类 ... -
Benchmark
2010-06-17 14:10 8941,length > 0和blank?和emtpy? & ... -
ruby的笔记
2010-05-20 14:23 948最近看了看ruby元编程的一些东西。简单的记下。 1,ruby ... -
闭包(回顾,转载)
2010-03-22 23:02 829闭包的一个重要特征是:过程(方法)内部定义的变量,即使在方法调 ... -
ruby cookbook -- 10.7检查对象是否具有必需的属性
2010-03-01 23:51 781检查是否具有实例变量 class Object de ... -
ruby cookbook -- 10.6. Listening for Changes to a Class监听类的变化
2010-03-01 23:30 780当增加新方法,类方法删除和取消定义的现有方法 class T ... -
ruby cookbook -- 10.4Getting a Reference to a Method(获得方法引用)
2010-03-01 23:25 818A Method object can be stored ... -
irb配置
2010-02-24 13:21 1081#.irbrc require 'rubygems' ... -
ruby cookbook -- 使分配程序能够使用注册回调的返回值
2010-02-23 19:23 788#使分配程序能够使用注册回调的返回值 A simple cha ...
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