From: Trans <transfire@...>
Date: 2007-10-15T19:43:29+09:00
Subject: Re: nil.to_i returning zero



On Oct 15, 6:27 am, "Robert Dober" <robert.do...@gmail.com> wrote:
> On 10/15/07, Konrad Meyer <kon...@tylerc.org> wrote:
>
>
>
> > Quoth Michael Fellinger:
> > > On 10/15/07, Chad Perrin <per...@apotheon.com> wrote:
> > > > On Mon, Oct 15, 2007 at 04:40:35AM +0900, Gerardo Santana G?mez Garrido
> > wrote:
>
> > > > > What does nil.to_i return? Zero. And I wonder why. How can nil be
> > > > > interpreted as a number. It's beyond me.
>
> > > > There's been a few attempts to answer the question already.  I'm curious,
> > > > though:
>
> > > > What would you expect it to return, and why would you think that should
> > > > be the expected behavior?
>
> > > > Nothing immediately occurs to me as a better result of evaluating
> > > > nil.to_i than 0, within the context of the Ruby language, but if you have
> > > > an alternative view I'm open to learning from it.
>
> > > nil.to_i
> > > # > NoMethodError: undefined method `to_i' for nil:NilClass
> > > Integer(nil)
> > > # > TypeError: can't convert nil into Integer
>
> > > This is on my wish list for Christmas among other things.
>
> > Thing is, #to_i explicitly does *not* throw errors -- that's what Integer() is
> > for. Current (1.8.6) ruby doesn't error on Integer(nil) either, but IMO it
> > should.
>
> But Michael did not ask NilClass#to_i to throw an error, he did ask it
> to go away :)

If it goes away you get a NoMethodError.

> Now I am completely impartial on the behavior, but if nil.to_i is
> confusing for some folks it might be a good idea to put it away unless
> other folks really need it.
> My pragmatic question is therefore:
> nil.to_i usecases anyone?

  def any_method(want_an_integer=nil)
    @want_an_integer = want_an_integer.to_i
    @want_an_integer + 1  # ... whatever ...
  end

It is generally better to use nil for default parameters b/c it
reduces the potential for errors and increases the flexability of the
design. The same is true of using "to_i". If you did it otherwise:

  def any_method(want_an_integer=0)
    @want_an_integer = want_an_integer
    @want_an_integer + 1
  end

Errors would occur on calling:

  any_method(nil)

and

 any_method("0")

And to compensate one would have to put the flexability into the call:

  any_method((some_var || 0).to_i)

Which IMO, is much less desirable.

T.