Re: Noob question regarding custom method

On Mon, Nov 14, 2011 at 1:29 PM, Sam Rose <[e-mail]> wrote:
> "setter" methods that have "set" in the name are far more idiomatic of
> Java. Ruby has a different way of doing this:
>
> def miles=3D(new_miles)
> =A0@miles =3D new_miles
> end
>
> Which I know wasn't the question, I just felt like mentioning this first =
:)
>
> You're right, you could use attr_accessor (or reader or writer,
> whichever suits the purpose best). And in this case, you probably
> would. There's no reason not to. But some setter methods require, for
> example, some kind of validation.
>
> Say if you didn't want the @miles variable to be less than 0, you could d=
o this:
>
> def miles=3D(new_miles)
> =A0if new_miles < 0
> =A0 =A0raise Exception, "Miles cannot be less than 0."
> =A0else
> =A0 =A0@miles =3D new_miles
> =A0end
> end
>
> Is this making sense? :)

Just a stylistic remark: I would code it like this

def miles=3D(new_miles)
  if new_miles < 0
    raise Exception, "Miles cannot be less than 0."
  end

  @miles =3D new_miles
end

or even

def miles=3D(new_miles)
  raise Exception, "Miles cannot be less than 0." if new_miles < 0

  @miles =3D new_miles
end

or

def miles=3D(new_miles)
  new_miles < 0 and raise Exception, "Miles cannot be less than 0."

  @miles =3D new_miles
end

Especially with the first variant it is immediately clear what the
main course of action is.  The exception interrupts the regular flow
anyway so there is really no reason for the "else" branch.

Kind regards

robert

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