From: Colin Bartlett <colinb2r@...>
Date: 2010-09-03T05:12:36+09:00
Subject: Re: selecting a variable number of individual items

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On Thu, Sep 2, 2010 at 8:38 PM, Joe Pizzanley <pizzazjoe@yahoo.com> wrote:

> Colin Bartlett wrote:
> > I'm a bit hesitant to suggest this because you've been studying Ruby a
> > long time,
> you're assuming that I've gotten good at it. It's still confusing to me
> in many spots.
>
> > and because I don't think I understand sufficiently what you want to do.
> the second half of your sentence is proof that I haven't gotten good at it.
>
Well, there is a difference between not knowing what you want to do, and
knowing what you want to do but not be able to explain what you want to do!
:)

>
> However your solution gave me enough to go on. I can push the arguments
>  into an array and then iterate through selecting whatever is in the array.
> thanks for extending help Colin! Much appreciated.
>
No trouble: I wasn't sure what level to pitch any explanation at, and the
examples were aimed at what I thought you wanted to do - it seems that I
wasn't all that far off?

The following is a very simplified explanation of Ruby method arguments,
targetted at want you want to do. There's a longer (not quite up-to-date -
Ruby 1.9 allows more method argument options) explanation here:
http://ruby-doc.org/docs/ProgrammingRuby/html/tut_methods.html

class VarArgsExample
# example showing compulsory arguments, default arguments,
 # and variable length arguments
  def example_meth( arg0, arg1, arg2 = 222, arg3 = 333, *args )
    puts "0=#{arg0.inspect}, 1=#{arg1.inspect}," \
    " 2=#{arg2.inspect}, 3=#{arg3.inspect};" \
    " var len args= #{args.inspect};"
    "return value"
  end
end

obj = VarArgsExample.new

obj.example_meth( ) rescue (p $!)
#=> #<ArgumentError: wrong number of arguments (0 for 2)>
obj.example_meth( 'apple' ) rescue (p $!)
#=> #<ArgumentError: wrong number of arguments (1 for 2)>
obj.example_meth( 'apple', 'fig' )
#=> 0="apple", 1="fig", 2=222, 3=333; var len args=[]
obj.example_meth( 'apple', 'fig', 'lemon' )
#=> 0="apple", 1="fig", 2="lemon", 3=333; var len args=[]
obj.example_meth( 'apple', 'fig', 'lemon', 'grape' )
#=> 0="apple", 1="fig", 2="lemon", 3="grape"; var len args=[]
obj.example_meth( 'apple', 'fig', 'lemon', 'grape', 'cherry' )
#=> 0="apple", 1="fig", 2="lemon", 3="grape"; var len args=["cherry"]
obj.example_meth( 'apple', 'fig', 'lemon', 'grape', 'cherry', 'blossom' )
#=> 0="apple", 1="fig", 2="lemon", 3="grape"; var len args=["cherry",
"blossom"]

For what you want do you can just do:
  def select_values( *args )
    # array args holds all the arguments passed to this method;
    # and if you want to trap if no arguments were passed then
    if args.size == 0 then
      raise "select_values must have at least one argument"
    end
  end

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