Ruby -如何填充2d数组？

Question

我有一个rspec测试：

  it 'has a populated chessboard' do
    expect(ChessBoard.new.populate_new_board).to eq [
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn'],
      ['pawn','pawn','pawn','pawn','pawn','pawn','pawn','pawn']]

  end

对于此代码：

class ChessBoard

  def initialize
    @board=Array.new(7){Array.new(7)}
  end

  def populate_new_board
    (0..7).each do |row|
      (0..7).each do |cell|
        @board[row][cell]='pawn'
      end
    end
    @board
  end

end

但我得到了：

  1) least number of moves from x to y has a populated chessboard
     Failure/Error: expect(ChessBoard.new.populate_new_board).to eq [
     NoMethodError:
       undefined method `[]=' for nil:NilClass
     # ./code.rb:10:in `block (2 levels) in populate_new_board'
     # ./code.rb:9:in `each'
     # ./code.rb:9:in `block in populate_new_board'
     # ./code.rb:8:in `each'
     # ./code.rb:8:in `populate_new_board'
     # ./code_spec.rb:12:in `block (2 levels) in <top (required)>'

我怎么才能解决这个问题？

顺便说一下，每个空间中的棋子不是最终的结果，但这正是我现在想要的测试结果(然后我可以进一步修改它)。

Answer 1

改为：

def populate_new_board
  (0...7).each do |row|
    (0...7).each do |cell|
      @board[row][cell]='pawn'
    end
  end
  @board
end

Answer 2

class ChessBoard
   def populate_new_board
      @board = [['pawn'] * 7] * 7
   end
end

Answer 3

因为它表示您在范围内做了一个错误，但是强烈建议您减少索引范围的使用。您可以使用:each和:map方法来代替：

class ChessBoard
   def initialize
      @board = Array.new( 7 ){ Array.new( 7 ) }
   end

   def populate_new_board
      @board.each {| row | row.map! {| _ | 'pawn' } }
   end
end

但我会使用更多的简单代码：

class ChessBoard
   def populate_new_board
      @board = Array.new( 7 ){Array.new( 7 ) { 'pawn' } }
   end
end