tiles.rb

class TileWithNeighbours
    @@instances = []
    attr_accessor :instances
    def initialize(filename, **neighbours)
        @filename = filename 
        @neighbours = neighbours
        @@instances << self
    end 
    attr_accessor :filename
    attr_accessor :neighbours
    def matches(**neighbours)
        neighbours.default_proc = proc do |hsh,k| @neighbours[k] end
        @neighbours.each do |direction, type|
            if type != neighbours[direction]
                return false
            end 
        end 
        return true
    end 
    def self.fit_with(**neighbours)
        @@instances.select { |tile| tile.matches(**neighbours) }
    end 
    def to_s
        "#{@filename} with #{@neighbours}"
    end 
end 

boo = TileWithNeighbours.new('boo', :north => :trees)
foo = TileWithNeighbours.new('foo', :north => :grass, :east => :trees, :south => :trees)

puts TileWithNeighbours.fit_with(:south => :trees) # boo, foo