Thanks Cliff and Steve - legends!
def eql?(other)
[name].eql?([other.name])
end
def hash
[name].hash
end
http://www.ruby-forum.com/topic/165653
Sonia Hamilton.
Steve Hoeksema wrote:
> Try "eql?"
>
> see
> http://stackoverflow.com/questions/372652/what-are-the-ruby-gotchas-a-newbie-should-be-warned-about/392774#392774
>
> On Fri, Aug 28, 2009 at 4:02 PM, Sonia Hamilton <[email protected]
> <mailto:[email protected]>> wrote:
>
>
> Hi everyone,
>
> My question is more about Ruby than Rails...
>
> I've got arrays of objects and I'm trying to do array differences.
> What
> do I need to override in my objects for array differences to work?
> (where I want equality based on attributes not object ids) I
> thought it
> was == but it doesn't seem to be working - please hit me with a clue
> stick :-)
>
> A bit more detail:
>
> Using simple arrays you can do array differences (and additions,
> unions,
> etc):
>
> >> a1 = %w[a b]
> >> a2 = %w[a c]
> >> a1 - a2
> => ["b"]
>
> Using a class like this:
>
> class Host
> attr_accessor :name
> def initialize(hostname)
> @name = hostname + '.company.com.au <http://company.com.au>'
> end
> def ==(h)
> @name == h.name <http://h.name>
> end
> end
>
> I would've thought differences of arrays of Hosts would then work,
> but no:
>
> >> hosts = [ Host.new('a'), Host.new('b') ]
> => [#<Host:0xb705b5ec @name="a.company.com.au
> <http://a.company.com.au>">, #<Host:0xb705b588
> @name="b.company.com.au <http://b.company.com.au>">]
> >> hosts2 = [ Host.new('a'), Host.new('c') ]
> => [#<Host:0xb7057fc8 @name="a.company.com.au
> <http://a.company.com.au>">, #<Host:0xb7057f64
> @name="c.company.com.au <http://c.company.com.au>">]
> >> p hosts - hosts2
> [#<Host:0xb705b5ec @name="a.company.com.au
> <http://a.company.com.au>">, #<Host:0xb705b588
> @name="b.company.com.au <http://b.company.com.au>">]
>
> The == is however working:
>
> >> h1 = Host.new('a')
> => #<Host:0xb7086800 @name="a.company.com.au
> <http://a.company.com.au>">
> >> h2 = Host.new('a')
> => #<Host:0xb7084a28 @name="a.company.com.au
> <http://a.company.com.au>">
> >> h1 == h2
> => true
>
> --
> Sonia Hamilton.
>
>
>
>
>
>
> --
> Steve Hoeksema
> +61 404 938 816
>
> >
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