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robo

2010-Apr-27 23:58 UTC

Locational relationship?

ok, I''ve got a model called Location, the idea being that i have a
bunch of locations aligned to a grid.  Each location has a pointer to
it''s neighbors, like so

create_table "locations", :force => true do |t|
    t.string   "name"
    t.text     "description"
    t.integer  "north"
    t.integer  "northeast"
    t.integer  "east"
    t.integer  "southeast"
    t.integer  "south"
    t.integer  "southwest"
    t.integer  "west"
    t.integer  "northwest"
    t.integer  "x"
    t.integer  "y"
    t.datetime "created_at"
    t.datetime "updated_at"
    t.integer  "map_id"
  end

whereas all the directions (north, south, east, etc) should all be
references to other locations.

I know this is probably an easy question, but what kind of
relationship is this, and how would I set it up in my model?  like
this?

has_one :location, :foreign_key => :north
has_one :location, :foreign_key => :northeast
has_one :location, :foreign_key => :east
has_one :location, :foreign_key => :southeast
has_one :location, :foreign_key => :south
has_one :location, :foreign_key => :southwest
has_one :location, :foreign_key => :west
has_one :location, :foreign_key => :northwest

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Sharagoz

2010-Apr-28 06:19 UTC

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Re: Locational relationship?

This is a self referential association

class Location <  ActiveRecordBase
   has_one :south, :class_name => ''Location'', :foreign_key
=> ''south''
end

On Apr 28, 1:58 am, robo
<chase.delanguille...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> ok, I''ve got a model called Location, the idea being that i have a
> bunch of locations aligned to a grid.  Each location has a pointer to
> it''s neighbors, like so
>
> create_table "locations", :force => true do |t|
>     t.string   "name"
>     t.text     "description"
>     t.integer  "north"
>     t.integer  "northeast"
>     t.integer  "east"
>     t.integer  "southeast"
>     t.integer  "south"
>     t.integer  "southwest"
>     t.integer  "west"
>     t.integer  "northwest"
>     t.integer  "x"
>     t.integer  "y"
>     t.datetime "created_at"
>     t.datetime "updated_at"
>     t.integer  "map_id"
>   end
>
> whereas all the directions (north, south, east, etc) should all be
> references to other locations.
>
> I know this is probably an easy question, but what kind of
> relationship is this, and how would I set it up in my model?  like
> this?
>
> has_one :location, :foreign_key => :north
> has_one :location, :foreign_key => :northeast
> has_one :location, :foreign_key => :east
> has_one :location, :foreign_key => :southeast
> has_one :location, :foreign_key => :south
> has_one :location, :foreign_key => :southwest
> has_one :location, :foreign_key => :west
> has_one :location, :foreign_key => :northwest
>
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Marnen Laibow-Koser

2010-Apr-28 13:20 UTC

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Re: Locational relationship?

robo wrote:> ok, I''ve got a model called Location, the idea being that i have a
> bunch of locations aligned to a grid.  Each location has a pointer to
> it''s neighbors, like so
> 
> create_table "locations", :force => true do |t|
>     t.string   "name"
>     t.text     "description"
>     t.integer  "north"
>     t.integer  "northeast"
>     t.integer  "east"
>     t.integer  "southeast"
>     t.integer  "south"
>     t.integer  "southwest"
>     t.integer  "west"
>     t.integer  "northwest"
>     t.integer  "x"
>     t.integer  "y"
>     t.datetime "created_at"
>     t.datetime "updated_at"
>     t.integer  "map_id"
>   end
> 
> whereas all the directions (north, south, east, etc) should all be
> references to other locations.
> 
> I know this is probably an easy question, but what kind of
> relationship is this, and how would I set it up in my model?  like
> this?
> 
> has_one :location, :foreign_key => :north
> has_one :location, :foreign_key => :northeast
> has_one :location, :foreign_key => :east
> has_one :location, :foreign_key => :southeast
> has_one :location, :foreign_key => :south
> has_one :location, :foreign_key => :southwest
> has_one :location, :foreign_key => :west
> has_one :location, :foreign_key => :northwest
I think I would avoid this.  If the grid is regular, then you should 
probably just store the X and Y coordinates in the model, then do 
something like

class Location < AR::B
  def northeast
    @northeast ||= Location.find_by_x_and_y(x + 1, y + 1)
  end
end

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

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robo

2010-Apr-28 15:00 UTC

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Re: Locational relationship?

Is there a reason why you would avoid setting up an association for
each one?  It seems like it''s basically the exact same thing you
proposed, but a little more long-winded.  No offense meant :)

I mean what difference does it make if I create an association that
finds its neighbors vs. writing a method that ends up finding the
neighbors manually?

On Apr 28, 8:20 am, Marnen Laibow-Koser
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:> robo wrote:
> > ok, I''ve got a model called Location, the idea being that i
have a
> > bunch of locations aligned to a grid.  Each location has a pointer to
> > it''s neighbors, like so
>
> > create_table "locations", :force => true do |t|
> >     t.string   "name"
> >     t.text     "description"
> >     t.integer  "north"
> >     t.integer  "northeast"
> >     t.integer  "east"
> >     t.integer  "southeast"
> >     t.integer  "south"
> >     t.integer  "southwest"
> >     t.integer  "west"
> >     t.integer  "northwest"
> >     t.integer  "x"
> >     t.integer  "y"
> >     t.datetime "created_at"
> >     t.datetime "updated_at"
> >     t.integer  "map_id"
> >   end
>
> > whereas all the directions (north, south, east, etc) should all be
> > references to other locations.
>
> > I know this is probably an easy question, but what kind of
> > relationship is this, and how would I set it up in my model?  like
> > this?
>
> > has_one :location, :foreign_key => :north
> > has_one :location, :foreign_key => :northeast
> > has_one :location, :foreign_key => :east
> > has_one :location, :foreign_key => :southeast
> > has_one :location, :foreign_key => :south
> > has_one :location, :foreign_key => :southwest
> > has_one :location, :foreign_key => :west
> > has_one :location, :foreign_key => :northwest
>
> I think I would avoid this.  If the grid is regular, then you should
> probably just store the X and Y coordinates in the model, then do
> something like
>
> class Location < AR::B
>   def northeast
>     @northeast ||= Location.find_by_x_and_y(x + 1, y + 1)
>   end
> end
>
> Best,
> --
> Marnen Laibow-Koserhttp://www.marnen.org
> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
> --
> Posted viahttp://www.ruby-forum.com/.
>
> --
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Rails - Apr 2010 - Locational relationship?

Locational relationship?

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Re: Locational relationship?