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Ruby: Refactoring a complicated method of nested loop

 3 years ago
source link: https://www.codesd.com/item/ruby-refactoring-a-complicated-method-of-nested-loop.html
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Ruby: Refactoring a complicated method of nested loop

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I'm trying to get rid of duplication in my code. I have a method that populates a checkerboard with checkers:

def populate_checkers
  evens = [0, 2, 4, 6]
  odds  = [1, 3, 5, 7]

  0.upto(2) do |x_coord|
    if x_coord.even?
      evens.each do |y_coord|
        red_checker = Checker.new(x_coord, y_coord, :red)
        @board[x_coord][y_coord] = red_checker
      end
    elsif x_coord.odd?
      odds.each do |y_coord|
        red_checker = Checker.new(x_coord, y_coord, :red)
        @board[x_coord][y_coord] = red_checker
      end
    end
  end

  5.upto(7) do |x_coord|
    if x_coord.even?
      evens.each do |y_coord|
        black_checker = Checker.new(x_coord, y_coord, :black)
        @board[x_coord][y_coord] = black_checker
      end
    elsif x_coord.odd?
      odds.each do |y_coord|
        black_checker = Checker.new(x_coord, y_coord, :black)
        @board[x_coord][y_coord] = black_checker
      end
    end
  end
end

How can I remove duplication and still get the precise behavior I need?

You can try to extract a method and then extract a block into lambda. Then your code will be readable and loose of duplication

def populate_checkers
  0.upto(2) do |x_coord|
    populate_checker(x_coord, :red)
  end

  5.upto(7) do |x_coord|
    populate_checker(x_cord, :black)
  end
end

def populate_checker(x_coord, color)
  evens = [0, 2, 4, 6]
  odds  = [1, 3, 5, 7]

  apply_checker = lambda do |y_coord|
   checker = Checker.new(x_coord, y_coord, color)
   @board[x_coord][y_coord] = checker
  end

  if x_coord.even?
    evens.each(&apply_checker)
  elsif x_coord.odd?
    odds.each(&apply_checker)
  end
end

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