Rails 1.2新特性体验(Hash，Integer和class)

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1 stringify_keys and symbolize_keys

>> { 'days' => 25, 'spirit' => 'giving', 'wallet' => 'empty' }.symbolize_keys
=> {:wallet=>"empty", :spirit=>"giving", :days=>25}
>> { 'system' => 'wii', :valid_ages => 5..90 }.stringify_keys
=> {"valid_ages"=>5..90, "system"=>"wii"}

2 assert_valid_keys 方法判断参数的key值是否正确。
  User.find(:first, :with => {:active => 1})
  find没有:with key值。assert_valid_keys就能派上用处。

>> about_me = { :height => 71, :weight => 160, :likes => 'monster trucks'
=> {:height=>71, :likes=>"monster trucks", :weight=>160}
>> about_me.assert_valid_keys(:height, :weight, :age)
ArgumentError: Unknown key(s): likes 

3 diff 返回Hash改变或删除的部分

 >> name = { :first => 'Chris', :last => 'Wanstrath', :middle => 'Jebediah' }
=> {:first=>"Chris", :last=>"Wanstrath", :middle=>"Jebediah"}
>> name.diff(:first => 'Chris', :last => 'Wanstrath', :middle => 'Jonesy')
=> {:middle=>"Jebediah"}
>> name.diff(:first => 'Chris', :last => 'Wanstrath')
=> {:middle=>"Jebediah"} 

4 from_xml 把xml形式的字符串转换成hash对象

>> Hash.from_xml '1'
=> {"posts"=>{"post"=>{"id"=>"1"}}}  
>> Hash.from_xml '12'
=> {"posts"=>{"post"=>[{"id"=>"1"}, {"id"=>"2"}]}}

5 bytes, kilobytes, megabytes, gigabytes, terabytes, petabytes, and exabytes

>> 100.bytes
=> 100
>> 5.kilobytes
=> 5120
>> 10.megabytes
=> 10485760
>> 100.gigabytes
=> 107374182400
>> 2.terabytes
=> 2199023255552
>> 1.petabytes
=> 1125899906842624
>> 2.exabytes
=> 2305843009213693952  

6 seconds, minutes, hours, days, weeks, fortnights, months, years, ago / until, since / from_now

>> 15.seconds
=> 15
>> 2.minutes
=> 120
>> 30.hours
=> 108000
>> 1.days
=> 86400
>> 2.weeks
=> 1209600
>> 4.fortnights
=> 4838400
>> 2.months
=> 5184000
>> 17.years
=> 536479200
>> 2.days.ago
=> Sat Dec 16 00:34:49 -0800 2006
>> 2.days.ago(Time.now - 3.days)
=> Wed Dec 13 00:34:55 -0800 2006
>> 4.weeks.since("1985-03-13".to_time)
=> Wed Apr 10 00:00:00 UTC 1985  

7 ordinalize

>> 5.ordinalize
=> "5th"

8 even? 和 odd?判断是奇数还是偶数(multple_of?)

>> 2.even?
=> true
>> 2.odd?
=> false
>> 99.multiple_of? 60
=> false
>> 25.multiple_of? 5
=> true

9 group_by 有点类似sql里的group_by

>> magical_people = [ { :name => "Santa Claus",     :color => "Red" }, 
                      { :name => "Mrs Claus",       :color => "Red" }, 
                      { :name => "Twinkle the Elf", :color => "Green "} ]
=> [{:name=>"Santa Claus", :color=>"Red"}, {:name=>"Mrs Claus", :color=>"Red"}, {:name=>"Twinkle the Elf", :color=>"green "}]
>> magical_people.group_by { |person| person[:color] }
=> {"Green "=>[{:name=>"Twinkle the Elf", :color=>"green "}],
   "Red"=>[{:name=>"Santa Claus", :color=>"Red"}, {:name=>"Mrs Claus", :color=>"Red"}]}  

10 index_by 可以与上面方法对应。此方法是根据某一个key进行排序

>> beatles = [{ :first => 'John',  :last => 'Lennon' }, 
              { :first => 'Paul',  :last => 'McCartney' }, 
              { :first => 'Evan',  :last => 'Weaver' }, 
              { :first => 'Ringo', :last => 'Starr' }]
=> [{:first=>"John", :last=>"Lennon"}, {:first=>"Paul", :last=>"McCartney"}, {:first=>"Evan", :last=>"Weaver"}, {:first=>"Ringo", :last=>"Starr"}]
>> beatles.index_by { |beatle| beatle[:first] }
=> {"Evan"=>{:first=>"Evan", :last=>"Weaver"}, 
    "Paul"=>{:first=>"Paul", :last=>"McCartney"}, 
    "John"=>{:first=>"John", :last=>"Lennon"}, 
    "Ringo"=>{:first=>"Ringo", :last=>"Starr"}}

11 sum

>> [1,2,3,4,5].sum
=> 15
>> Recipe.find(:all).sum { |recipe| recipe.total_time.to_i }
=> 1777

12 alias_attribute 。为某一字段定义一个别名

class User < ActiveRecord::Base
  alias_attribute :user_id, :id
end

>> user = User.find(:first)
=> #
>> user.id
=> 1
>> user.user_id
=> 1
>> user.user_id?
=> true

13 attr_accessor_with_default方法重写了attr_accessor方法。在定义时给属性一个默认值。

class Homework
  attr_accessor_with_default :sucks, true 
end

>> assignment = Homework.new
=> #
>> assignment.sucks
=> true

14 class_inheritable_* 方法
只与类变量结合使用。class_inheritable_*定义的类变量不在父类和子类之间share。子类改变不会影响到父类。
class_inheritable_reader, class_inheritable_writer, class_inheritable_array_writer, class_inheritable_hash_writer, class_inheritable_accessor, class_inheritable_array, class_inheritable_hash

class Momma
  class_inheritable_hash :looks    
  self.looks = { :hair => 'blonde', :eyes => 'blue' }
end

class Kid < Momma
end

=> {:hair=>"blonde", :eyes=>"blue"}
>> Momma.looks
=> {:hair=>"blonde", :eyes=>"blue"}
>> Kid.looks
=> {:hair=>"blonde", :eyes=>"blue"}
>> Kid.looks.update :eyes => "brown" 
=> {:hair=>"blonde", :eyes=>"brown"}
>> Kid.looks
=> {:hair=>"blonde", :eyes=>"brown"}
>> Momma.looks
=> {:hair=>"blonde", :eyes=>"blue"}