From: Rong <ron.green@...>
Date: 2009-09-22T12:14:07+09:00
Subject: Re: start_with

Thanks David. I sent you a tweet.

On Sep 21, 9:23 pm, "David A. Black" <dbl...@rubypal.com> wrote:
> Hi --
>
> On Tue, 22 Sep 2009, Rong wrote:
> > Can someone explain why this doesn't work?
>
> > class Person
> >  attr_accessor :firstName
>
> >  P=[]
> >  def initialize
> >    P << self
> >  end
> >  def self.find_person(part)
> >    P.each {|e| if e.firstName.start_with(part) then return e end}
>
> You mean start_with? (with question mark).
>
> Also, you've got a bug. The #each method returns its receiver. That
> means that if nothing triggers the return inside the block, you'll get
> back the whole P array. See below....
>
> >    end
> >  end
>
> >  u=Person.new
> >  u.firstName="Ron"
> >  r=Person.new
> >  r.firstName="Bob"
>
> >  q=Person.find_person("Ro")
> >  puts q.firstName
>
> p Person.find_person("nobody")
>
> Output: [#<Person:0x1ee628 @firstName="Ron">, #<Person:0x1ee5d8
> @firstName="Bob">]
>
> What you want is:
>
>    def self.find_person(part)
>      P.find {|e| e.firstName.start_with(part) }
>    end
>
> which will return nil if nothing is found. (Also, first_name would be
> more idiomatic than firstName, as a variable name.)
>
> I've got reservations about using a constant as a modifiable array
> like you're doing, but one (or two) thing(s) at a time :-)
>
> David
>
> --
> David A. Black, Director
> Ruby Power and Light, LLC (http://www.rubypal.com)
> Ruby/Rails training, consulting, mentoring, code review
> Book: The Well-Grounded Rubyist (http://www.manning.com/black2)