Mazes for Programmers/

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Implementing a Polar Grid

Implementing a Polar Grid

Learn to implement a polar grid by introducing a new subclass in Ruby.

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Introduction

To implement this improved polar grid, we’re going to introduce a new Cell subclass in this lesson and then walk through how these new cells will be laid out and subdivided. We’ll finish it all off with one last, mostly aesthetic tweak to make our final maze as tidy as possible.

The PolarCell class

We’ve made it so far by using the existing Cell class, but it’s getting a bit difficult to keep referring to compass directions when they don’t map very intuitively to a polar grid. Also, with adaptive subdivision, some cells may now have two neighbors in the outward direction, and our existing Cell class has no support for that. Let’s create the subclass PolarCell.

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require 'cell'
class PolarCell < Cell
  attr_accessor :cw, :ccw, :inward 
  attr_reader :outward 
  def initialize(row, column)
    super
    @outward = [] 
  end
  def neighbors
    list = []
    list << cw if cw
    list << ccw if ccw
    list << inward if inward
    list += outward
    list
  end
end

Code explanation

Lines 4–5: We start things off by defining attributes for the polar directions: cw (clockwise), ccw (counterclockwise), inward (toward the origin), and outward (toward the rim).

Line 9: Note that line 5 only grants outward a reader, not a writer, because we won’t be assigning to it directly. Instead, in the constructor here, we initialize outward to be an empty array, and we’ll just append cells to it as needed.

With our new cell class ready, we can return to PolarGrid and start building on that a bit more.

Refactoring the Cell class

At this point, we might want to take some time to do a proper refactoring of Cell ...