game_of_life.rb

class Game
    attr_accessor :world, :seeds
    def initialize(world=World.new, seeds=[])
        @world = world
        @seeds = seeds
        seeds.each do |seed|
            world.cell_grid[seed[0]][seed[1]].alive = true
        end
    end

    def tick!
        next_round_dead = []
        next_round_alive = []
        @world.cells.each do |cell|
            count = self.world.live_neighbors_around_cell(cell).count
            if count < 2 && cell.alive?
                next_round_dead << cell
            end
            if (count == 2 || count == 3) && cell.alive?
                next_round_alive << cell
            end
            if  count> 3 && cell.alive?
                next_round_dead << cell
            end
            if count == 3 && cell.dead?
                next_round_alive << cell
            end
        end
        next_round_alive.each do |cell|
            cell.birth!
        end
        next_round_dead.each do |cell|
            cell.die!
        end
    end

end

class World
    attr_accessor :rows, :cols, :cell_grid, :cells
    def initialize(rows=3, cols=3)
        @rows = rows
        @cols = cols
        @cells = []


        @cell_grid = Array.new(rows) do |row|
                        Array.new(cols) do |col|
                            Cell.new(col, row)
                        end
                    end


        @cell_grid.each do |row|
            row.each do |element|
                if element.is_a?(Cell)
                    cells << element
                end
            end
        end
    end

    def live_neighbors_around_cell(cell)
        live_neighbors = []
        #neighbor to the north
        if cell.y > 0
            candidate = self.cell_grid[cell.y-1][cell.x]
            live_neighbors << candidate if candidate.alive?
        end
        #neighbor to the north east
        if cell.y>0 && cell.x < (@cols - 1)
            candidate = self.cell_grid[cell.y-1][cell.x+1]
            live_neighbors << candidate if candidate.alive?
        end
        #neighbor to the east
        if cell.x < (@cols - 1)
            candidate = self.cell_grid[cell.y][cell.x+1]
            live_neighbors << candidate if candidate.alive?
        end
        #neighbor to the south east
        if cell.y < (@rows- 1) && cell.x < ( @cols - 1)
            candidate = self.cell_grid[cell.y + 1][cell.x + 1]
            live_neighbors << candidate if candidate.alive?
        end
        #neighbor to the south
        if cell.y < (@rows- 1)
            candidate = self.cell_grid[cell.y + 1][cell.x]
            live_neighbors << candidate if candidate.alive?
        end        
        #neighbor to the south west 
        if cell.y < (@rows- 1) && cell.x > 0
            candidate = self.cell_grid[cell.y + 1][cell.x - 1]
            live_neighbors << candidate if candidate.alive?
        end
        #neighbor to the west
        if cell.x > 0
            candidate = self.cell_grid[cell.y][cell.x - 1]
            live_neighbors << candidate if candidate.alive?
        end
        #neighbor to the north west
        if cell.x > 0 && cell.y > 0
            candidate = self.cell_grid[cell.y - 1][cell.x - 1]
            live_neighbors << candidate if candidate.alive?
        end
        live_neighbors
    end

    def live_cells
        cells.select { |cell| cell.alive }
    end
    def randomly_populate
        cells.each do |cell|
            cell.alive = [true, false].sample
        end
    end
end

class Cell
    attr_accessor :alive, :x, :y

    def initialize(x=0, y=0)
        @alive = false
        @x = x
        @y = y
    end

    def alive?
        @alive
    end

    def dead?
        !@alive
    end

    def die!
        @alive = false
    end

    def birth!
        @alive = true
    end
end