From: Kent Dahl <kentda@...>
Date: 2002-08-09T06:23:21+09:00
Subject: Re: Variable validation

Chris Morris wrote:
> 
> I've got a class that has a number of instance variables, some of which must
> be set prior to calling a save function to write these off somewhere else.
> I'm doing the following:
> 
>       def check_required
>         if @password == nil or @password.empty?
>           or @firstName == nil or @firstName.empty?
>           or @lastName == nil or @lastName.empty?
>           or @nickName == nil or @nickName.empty?
>           or @email == nil or @email.empty?
>           raise RequiredDataMissingError('')
>       end
> 
> .. but this smells.

If all these are accessible from the outside in reader methods, you
could use an array of symbols and send:

<CODE>
class RequiredDataMissingError < Exception
end

class X
  MANDATORY_FIELDS = [ :password, :firstName, :lastName, 
    :nickName, :email ]
  
  attr_accessor *MANDATORY_FIELDS

  def check_required
    if MANDATORY_FIELDS.find{|field| 
	value = self.send(field)
	value == nil or value.empty?
      } then
      raise RequiredDataMissingError
    end
  end
end
</CODE>

This does add a methodcall indirection, which could hurt you
performancewise, but you seem to be (rightfully) trying to optimize for
eyeball time :-)

-- 
(\[ Kent Dahl ]/)_    _~_    __[ http://www.stud.ntnu.no/~kentda/ ]___/~
 ))\_student_/((  \__d L b__/  NTNU - graduate engineering - 5. year  )
( \__\_�|�_/__/ ) _)Industrial economics and technological management(
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