Initializing an array of instance variables

Question

I'm making a game with a Board class Cell class. The Board class needs to be initialized with a unique instance variable for each Cell. I can hardcode it so that it works, but it seems inelegant and doesn't allow the size of the board to be chosen by the user at runtime. Here's what I have:

class Board
  def initialize
    @cell_1 = Cell.new(1)
    @cell_2 = Cell.new(2)
    @cell_3 = Cell.new(3)
    @cell_4 = Cell.new(4)
    @cell_5 = Cell.new(5)
    @cell_6 = Cell.new(6)
    @cell_7 = Cell.new(7)
    @cell_8 = Cell.new(8)
    @cell_9 = Cell.new(0)
    @cells = [@cell_1, @cell_2, @cell_3,
              @cell_4, @cell_5, @cell_6,
              @cell_7, @cell_8, @cell_9]
  end
end

I think I could use a loop to create a hash with unique key names pointing to unique Cell objects, but I don't know how I could make unique instance variables with a loop.

falsetru · Accepted Answer · 2015-02-18 03:06:11Z

1

If you don't need to create each instance variables (@cell_1, @cell_2, ...), you can use Enumerable#map:

@cells = [*1..8, 0].map { |i| Cell.new(i) }

answered Feb 18, 2015 at 3:06

falsetru

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1 Comment

cks Over a year ago

I actually had been referring to each instance variable by their names and for some reason thought I needed to. It turns out I didn't. When I tried this and then switched the references (eg. @cells[0] instead of @cell_1), it worked. Thanks for your help.

Andrea · Accepted Answer · 2015-02-18 07:12:17Z

0

If you really need to refer every instance variable by name you can do something like this.

class Board
   def initialize
     @cells = (1..9).to_a.map { |i| Cell.new(i) }
   end

   def method_missing(method, *args, &block)
     if method =~ /^cell_[1-9][0-9]*$/
       index = method[/\d+/].to_i
       @cells[index-1]
     else
       super
     end
   end
end

In this way you can call:

board = Board.new
board.cell_1 #=> first cell

Of course I'd use the solution proposed by @falsetru.

edited Feb 18, 2015 at 7:12

answered Feb 18, 2015 at 7:06

Andrea

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