Ruby - 如何填充二维数组？答案

【问题标题】：Ruby - How to populate a 2d array?Ruby - 如何填充二维数组？
【发布时间】：2014-01-01 13:37:43
【问题描述】：

我有这个 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)>'

我该如何解决这个问题？

顺便说一句，每个空间中的棋子不是最终结果，但这是我现在想要的测试（然后我可以进一步修改它）。

【问题讨论】：

尝试填充为Array.new(7){Array.new(7) { 'pawn' } }
您最多索引 7 个而不是 6 个。

标签： ruby arrays rspec multidimensional-array

【解决方案1】：

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

【讨论】：

【解决方案2】：

改成：

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

【讨论】：

这显示了我的错误。最后，我实际上将初始化更改为用“8”调用。结果相同，数组大小内的迭代器

【解决方案3】：

正如您在范围内犯了一个错误，但强烈建议您减少索引范围的使用。您可以改用:each 和:map 方法：

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

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

但我会使用更多简单的代码：

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

【讨论】：