From: Walton Hoops <walton@...>
Date: 2010-01-21T06:36:40+09:00
Subject: Re: Looking for object.inherits?(Classname)

On 1/20/2010 12:05 PM, Xeno Campanoli wrote:
> Robert Klemme wrote:
>> 2010/1/20 Xeno Campanoli <xeno.campanoli@gmail.com>:
>>> I'm looking for a way to make sure an object being passed is in some 
>>> class
>>> family, or to say it otherwise, inherits some specific class, but not
>>> necessarily directly.  In fact, it could be a 
>>> great-great-grandparent class,
>>> and that would be okay, and needs to be okay.  Is there something 
>>> where I
>>> can take an object and go
>>>
>>> unless object.inherits?(MyClass)
>>>        raise SyntaxError, "etc."
>>> end
>>
>> First of all that would not be a SyntaxError because the syntax is not
>> affected.  Using this error type will create misleading error
>> messages.
>
> If I want a method that only takes objects of family Xclass, and I get 
> one passed that is not in that family, isn't that a syntax error?  Bad 
> type passed in that argument place?  What's the difference between 
> that and passing a string when it needs say an array?

Nope, that's an ArgumentError.  Example:
irb(main):001:0> Integer("boo")
ArgumentError: invalid value for Integer: "boo"
         from (irb):2
irb(main):002:0>

Integer("boo") syntactically correct, yet "boo" is not a valid argument 
for this function.