A class that looks like (kind_of?) several classes

ruby-talk
1

> Thanks. I assumed that the StringIO class inherited from
the
> IO class since it has all of the same methods. So the
proper
> Ruby style is to use respond_to? instead of kind_of? to see
> what "type" your arguments are?

The common Ruby style is to not check at all, but just send
the messages
needed to get the job done. If the object is inappropriate,
Ruby will
catch it and let you know what it didn't like.

I was referring to the case when a method does different things
based on the argument "types" (i.e. String#=). I'll just
start using "respond_to?" instead. I was using both.

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2

Hi --

Thanks. I assumed that the StringIO class inherited from

the

IO class since it has all of the same methods. So the

proper

Ruby style is to use respond_to? instead of kind_of? to see
what "type" your arguments are?

The common Ruby style is to not check at all, but just send
the messages
needed to get the job done. If the object is inappropriate,
Ruby will
catch it and let you know what it didn't like.

I was referring to the case when a method does different things
based on the argument "types" (i.e. String#=). I'll just
start using "respond_to?" instead. I was using both.

I think Jim was referring to that case too :slight_smile:

In a slightly oversimplified nutshell, you've got three main
possibilities:

   * class/module name/ancestry checking (kind_of?/is_a?)
   * type checking (respond_to?)
   * "duck typing" (what Jim described -- a programming technique
       in its own right, not a subdivision of checking)

I've listed them in increasing order of what I'd call resonance with
the underlying dynamism of Ruby objects. In a certain sense, in fact,
you're always doing duck typing when you send a message to an object
in Ruby, because you've agreed up front to work with objects whose
type can change during runtime.

"And etc.", as my students sometimes say. There's a ton more on this
in the archives... so I'll save a few electrons here :slight_smile:

David

···

On Wed, 11 May 2005, Eric Mahurin wrote:

--
David A. Black
dblack@wobblini.net