From: Paul McMahon <pm@...>
Date: 2008-04-03T14:30:46+09:00
Subject: Re: ruby constructor return value?

Brendan Stennett wrote:
> 
> In ruby..
> class Zip
>   def initialize(zipcode)
>     o = Zipcode.find_by_zipcode(zipcode)
>     if o.length == 0
>       return false
>     else
>       @zipcode = zipcode
>     end
>   end
> end
> 
> //then...
> if o = Zip.new('00000')
>   //this block execute whether or not that zip code exists
> else
>   //never happens
> end
> 
> ..now i know there are easier ways to do this, but its just an example
> to illustrate my point.

Maybe I'm missing something, but why not just push the creation into 
Zipcode.  I can't see why you would want to do this check in the 
constructor itself...

class Zipcode
   def self.find_by_zipcode(zipcode)
     zipcode = ... # query db
     if zipcode.length == 0
       nil
     else
       Zip.new(zipcode)
     end
   end
end

class Zip
   def initialize(zipcode)
     @zipcode = zipcode
   end
end

//then...
if o = Zip.find_by_zipcode('00000')
   // zipcode exists
else
   // doesn't exist
end