From: Avi Bryant <avi@...4.com>
Date: 2001-08-15T13:02:26+09:00
Subject: [ruby-talk:19757] Re: "new" returning nil: how to report the failure of object creation

On Wed, 15 Aug 2001, Ryo Furue wrote:

> Hi there,
> 
> How do you report the failure of object creation, that is, if you find
> it impossible to properly initialize the object in the "initialize"
> method?  Raising an exception is clearly an option.  But, what if the
> "failure" is a normal part of the flow of the program? as in
> 
>    class SomeClass
>       def initialize(file)
>          line = file.gets
>          if line
>             # initialize instance vars according to "line"
>          else
>             return nil ##<- a fictious Ruby feature
>          end
>       end
>    end

The easiest way is to override new instead; ie, something like:

class SomeClass
	def self.new(file)
		line = file.gets
		if line
			super(line)
		else
			nil
		end
	end

	def initialize(line)
		#initialize object
	end
end
			
avi