需要知道Ruby的...

以下都是在资料中摘抄下来的，有的目前还没有理解透，慢慢理解。

1、nil是对象（java中null不是对象)
2、整数是个完整的对象，如：3.abs
3、实例由类自己参建,通用工厂:

    def create_from_factory(factory)
      factory.new
    end

    obj = create_from_factory(Array) 

4、 Methods can be added to classes at any point，随处为类添加方法，下面是为Integer添加even?方法
   

class Integer
    def even?
        (self % 2) == 0
    end
end

p (1..10).select { |n| n.even? }
# => [2, 4, 6, 8, 10]

5、Singleton methods are defined on individual objects, not classes.

class Dog
end

rover = Dog.new
fido = Dog.new

def rover.speak
    puts "Red Rover"
end

rover.speak # => "Red Rover"
fido.speak # => NoMethodError

5、Lanaguage Typing Systems

Java is

• Strongly,
• Statically,
• Manifestly

typed.

Ruby is

• Strongly,
• Dynamically,
• Implicitly

typed.