Li Yafei
A senior Ruby on Rails developer
rEFINE in ruby
szRubyists Meetup 12th
by WinDy
ABOUT me
正宗Ruby玩家
就职于一家网络公司
三年经验
野路子
杂
就职于一家网络公司
三年经验
野路子
杂
联系方式请在这里找: http://who.yafeilee.me
Try MONKEY-PATCH
class Fixnum
alias old_plus +
def +(o)
old_plus(o).old_plus(o)
end
end
puts 1+1 # output is 3
MONKEY-patch in REAL WORLD
require 'rubygems'
require 'active_support'
require 'active_support/core_ext'
puts [1,2].second # output is 2
PRoblem
一剑封喉
走火入魔
如履薄冰
信春哥，坑队友
......
Refine COMING
module R
refine String do
def camelize(o)
"ABC"
end
end
end
class K
using R
puts "a".camelize # got ABC
end
puts "a".camelize # no method error
REFINE
so easy...
REFINE
I don't think so...
rEFINE
do you know
module_eval ?
class Baz < Quux
def up_and_add(str1, str2)
str1.upcase + str2.upcase
end
end
Really so simple ?
REFINE
module BadRefinement
refine String do
def upcase
reverse
end
end
end
class Quux
using BadRefinement
end
class Baz < Quux
def up_and_add(str1, str2)
str1.upcase + str2.upcase
end
end
REFINE
real MAGIC!!!
REFINE
real "COOL" ?
REFINE
Oh no, BAD thing agian!
REFINE
封装性
歧义
行为一致性
REFINE
All Broken!!!
REFINE WITH
MODULE_EVAL
def add_all(str_ary)
str_ary.inject('') do |str, accum|
accum + str
end
end
仅仅是 "字符串连接吗" ?
不要忘了
module_eval
REFINE WITH
MODULE_EVAL
module WeirdPlus
refine String do
def +(other)
"#{self} plus #{other}"
end
end
end
class MyArray
def initialize
@ary = ['foo', 'bar', 'baz']
end
def inject(accum, &block)
@ary.each do |str|
accum = WeirdPlus.module_exec(str, accum, &block)
end
accum
end
end
实现的问题
- 当前上下文(lexical scope)
- 调用者上下文(inherit scope)
附: Method Search
METhoD SEARCH E.G.
class A
def self.a
puts 'a'
end
class << self
a # wrong
end
end
class B < A
a # right
end
constant lookup
module A
module B; end
module C
module D
B == A::B
end
end
end
surrounding lexical scope
CONSTANT LOOKUP
module A
module C
module D
Module.nesting == [A::C::D, A::C, A]
end
end
end
CONSTANT LOOKUP TESTING
module M1
CT = "ok"
end
class C1
CK = "ck"
include M1
def self.method1
puts self
puts "#{CK} in method1"
puts "#{CT} in method1"
end
class << self
def method2
puts self
puts "#{CK} in method1"
puts "#{CT} in method2"
end
end
end
C1.method1 # here is ok ?
C1.method2 # what will happen ?
CONSTANT LOOKUP SUMMARY
- Lookup lexical scope
- if not, lookup ancestors scope
so easy, isn't it ? yes, but not really.
CLASS_EVAL
class A
module B; end
end
class C
module B; end
puts A.class_eval { B } == A::B
end
true or false ?
CLASS_EVAL
class A
module B; end
end
class C
module B; end
puts A.class_eval("B") == A::B
end
true or false ?
READ MORE
C语言足够好？ 看这个：
解决之道
- 去掉 module_eval 对 refine 的支持
- 限制 using 的支持范围:
- using 限定为关键字
- using 只允许在类中使用
回顾
- module_eval带来的问题
- 限制using
当前的实现
Ruby2.0.0-preview1
当前的实现
Ruby2.0.0-preview2
IN the LATER
- refinements are file scope
- only top-level "using" is available
- no module scope refinements
- no refinements inheritance
- module_eval do not introduce refinement
BUT IN the future
激烈讨论中：
总结
- DON'T HARM.
- 隔离作用域.
- 理解背后的原理.
- BUT... please don't use it now.
QA
Any Question?
Thx.
THANKS
[Charles Nutter](http://blog.headius.com/2012/11/refining-ruby.html)
中译版:
refine in ruby
By Li Yafei
