Ruby self.to_enum 求解疑
《The Ruby Programming Language》5.3.4 Enumerators 这一节中有段代码
def twice
if block_given?
yield
yield
else
self.to_enum(:twice)
end
end
没看懂，原文中说
You can duplicate this behavior in your own iterator methods by returning self.to_enum when no block is supplied. Here, for example, is a version of the the twice iterator shown earlier that can return an enumerator if no block is provided:
但是这样写有什么实际意义吗？
没有 else 你只能这样用，twice { do somethoing }
上面 else 这样写了之后你可以这样用，e = twice； e.each { do something }