导致随机TypeError的Proc

Question

我正在重构一些代码，这个proc随机地导致了一个错误，我不知道为什么或者如何调试它.有什么想法吗？

使用proc的新代码

  defense_moves, offense_moves = [], []
  determine_move = ->move,side,i { side << move.count(move[i]) }
  defense.size.times { |i| determine_move.(defense, defense_moves, i) }
  offense.size.times { |i| determine_move.(offense, offense_moves, i) }
  dm = defense[defense_moves.index(defense_moves.max)].nil? ? [0] : defense[defense_moves.index(defense_moves.max)]
  om = offense[offense_moves.index(offense_moves.max)].nil? ? [0] : offense[offense_moves.index(offense_moves.max)]

原始代码：

  d = 0
  defense_moves = []
  loop do 
    defense_moves << defense.count(defense[d])
    break if defense.count(defense[d]).zero?
    d += 1
  end

  o = 0
  offense_moves = []
  loop do 
    offense_moves << offense.count(offense[o])
    break if offense.count(offense[o]).zero?
    o += 1
  end

  dm = defense[defense_moves.index(defense_moves.max)].nil? ? [0] : defense[defense_moves.index(defense_moves.max)]
  om = offense[offense_moves.index(offense_moves.max)].nil? ? [0] : offense[offense_moves.index(offense_moves.max)]

TypeError

ttt2.rb:95:in `[]': no implicit conversion from nil to integer (TypeError)
    from ttt2.rb:95:in `computer_make_move'
    from ttt2.rb:133:in `draw_board'
    from ttt2.rb:24:in `place'
    from ttt2.rb:209:in `block in start_new_game'
    from ttt2.rb:188:in `loop'
    from ttt2.rb:188:in `start_new_game'
    from ttt2.rb:199:in `block in start_new_game'
    from ttt2.rb:188:in `loop'
    from ttt2.rb:188:in `start_new_game'
    from ttt2.rb:199:in `block in start_new_game'
    from ttt2.rb:188:in `loop'
    from ttt2.rb:188:in `start_new_game'
    from ttt2.rb:199:in `block in start_new_game'
    from ttt2.rb:188:in `loop'
    from ttt2.rb:188:in `start_new_game'
    from ttt2.rb:199:in `block in start_new_game'
    from ttt2.rb:188:in `loop'
    from ttt2.rb:188:in `start_new_game'
    from ttt2.rb:234:in `<main>'

Answer 1

所以，在代码出现之前：

defense_moves, offense_moves = [], []
determine_move = -> move, side, i { side << move.count(move[i]) }
(defense.size + 1).times { |i| determine_move.(defense, defense_moves, i) }
(offense.size + 1).times { |i| determine_move.(offense, offense_moves, i) }
dm = defense[defense_moves.index(defense_moves.max)].nil? ? [0] : defense[defense_moves.index(defense_moves.max)]
om = offense[offense_moves.index(offense_moves.max)].nil? ? [0] : offense[offense_moves.index(offense_moves.max)]

(defense/offence.size + 1)，原因中断是在添加到数组之后。

我不确定它是否正确，但我想它的工作原理与那个循环相同。

Answer 2

loop do 
  defense_moves << defense.count(defense[d])
  ...
end

保证至少为defense_moves分配一个元素。

determine_move = ->move,side,i { side << move.count(move[i]) }
defense.size.times { |i| determine_move.(defense, defense_moves, i) }

没有提供这样的保证。因此，defense_moves.max和defense_moves.index(defense_moves.max)都是零，这会产生错误。

Answer 3

您的错误消息意味着要将零传递给[]方法。我猜它就在这条线上

defense[defense_moves.index(defense_moves.max)]

或者另一个类似的。

如果defense_moves是空数组，则[].max #=> nil，如果您传递defense[nil]，则会收到该错误。