From: Robert Klemme <bob.news@...>
Date: 2004-04-24T18:39:05+09:00
Subject: Re: Problem assigning an Array object to an Array-subclass object


"Richard Lionheart" <NoOne@Nowhere.com> schrieb im Newsbeitrag
news:iLSdne99T7Y0rhTdRVn-jw@comcast.com...
> [ I apologize if this is a second post.  My earlier one seems to have
gotten
> lost in the ethernet :-) ]
>
> notes =<<NOTES
>     I didn't like to_s' output for an Array of strings.
>     Array#to_s simply concatenated them
>     or inserted a comma separator.
>     So I wrote my own.
>     But as the last line indicates,  I failed.
>
>     Apparently, array assignment to myA1
>     changed the reference from a MyArrayType object
>     to an Array object.
>
>     Two questions:
>     1.  How can I set myA1 to an array value
>         and preserve it's type?
>     2.  Isn't there a "Ruby way" to set the separator
>     (I thought there was some special symbol a la Perl
>     but I couldn't find any in Thomas' or Fulton's
>     books.)
> NOTES
>
> class MyArrayType < Array
>     def to_s
>         print "Starting MyArrayType#to_s"
>         s = ""
>         s.each { |x| s += "; " if s.length>0; s += x.to_s }
>         s
>     end
> end
>
> myA1 = MyArrayType.new
> myA1 = %w[x1, y1]

There seems to be a misunderstanding on your side about variables, objects
and types.  Variables do not have a type, they just hold references to any
object.  So your code does not declare a variable "myA1" of type
MyArrayType, it merely first assigns the result of MyArrayType.new (a new
instance of class MyArrayType) and then assigns the result of %w[x1, y1] to
myA1, loosing the reference to the MyArrayType instance.

Simply use Array#join:

irb(main):014:0> %w[x1, x2].join( '; ' )
=> "x1,; x2"

Note: the ',' is part of the first word.  You probably wanted

irb(main):015:0> %w[x1 x2].join( '; ' )
=> "x1; x2"

Regards

    robert