From: Ezra Zygmuntowicz <ezmobius@...>
Date: 2006-12-21T07:05:40+09:00
Subject: Re: reflecting on objects without creating one


On Dec 20, 2006, at 1:53 PM, Justin Bailey wrote:

> On 12/20/06, _Kevin <kevin.olbrich@gmail.com> wrote:
>>
>> Let's say I have two constants
>>
>> a = Integer
>> b = Numeric
>>
>> Does anyone have any idea how to see if 'a' is a subclass of 'b'
>> WITHOUT creating an object of class 'a'?
>
>
> irb(main):021:0> a = Numeric
> => Numeric
> irb(main):022:0> b = Integer
> => Integer
> irb(main):023:0> a.ancestors
> => [Numeric, Comparable, Object, Kernel]
> irb(main):024:0> a.ancestors.include? b
> => false
> irb(main):025:0> b.ancestors.include? a
> => true
> irb(main):026:0>
>
> "b.ancestors.include? a" seems to do it. Notice I reversed your  
> definitions
> of "a" & "b" (not for any particular reason, that's just how it  
> worked out).
>
> Justin

You can also use < and > to compare subclasses or superclasses

ez $ irb
 >> a = Integer
# => Integer

 >> b = Numeric
# => Numeric

 >> a < b
# => true

 >> a > b
# => false


Cheers-

-- Ezra Zygmuntowicz 
-- Lead Rails Evangelist
-- ez@engineyard.com
-- Engine Yard, Serious Rails Hosting
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