[技巧]Include与Extend的比较
本帖最后由 2gua 于 2010-12-07 11:36 编辑你可以用include或extend来MixIn（混入）module的方法到class。
它俩的不同在于：
include使得module的方法被类实例使用；
extend使得module的方法被类本身使用。
举例：
module Greetings
def say_hello
puts "Hello!"
end
end
class Human
include Greetings
end
Human.new.say_hello # => "Hello!"
Human.say_hello # NoMethodError
class Robot
extend Greetings
end
Robot.new.say_hello # NoMethodError
Robot.say_hello # => "Hello!"
如果你想了解更多关于include和extend比较的信息，推荐你看看以下资源：
[*]What is the difference between include and extend in Ruby? on Stack Overflow.[*]Include vs Extend in Ruby by John Nunemaker[*]Ruby extend and include by Jay Fields
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