From: Walton Hoops <walton@...>
Date: 2010-01-21T06:54:22+09:00
Subject: Re: Looking for object.inherits?(Classname)

On 1/20/2010 2:36 PM, Walton Hoops wrote:
> 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.
>
Whoops, my bad, actually the situation you describe is a TypeError:
irb(main):002:0> Integer([1,2,3])
TypeError: can't convert Array into Integer
         from (irb):3
irb(main):003:0>

again, still syntactically sound, but Integer can't take an array.