我 运行 遇到 'split' for nil:NilClass in ruby 的错误，即使它只是工作

Question

我正在处理一些我很难弄清楚的代码，然后突然出现这个错误说：

in `process_data': undefined method `split' for nil:NilClass (NoMethodError)

所以我撤消了我所做的更改，它一次又一次地弹出，我对导致它的原因一无所知？
代码

class HiScore
    attr_reader :hiscore

    def initialize
        @hiscore = if File.exist?('hiscore.txt')
            read_file
        else
            build_new
        end
    end

    def show
        puts "Top 5 Scores"
        @hiscore.each do |r|
          puts r.each { |p| p }.join(" ")
        end
    end

    def build_new
        Array.new(5) {[1000, '--']}
        write_file()
    end

    def read_file()
        puts "read_file"
        #File.open('hiscore.txt', 'r') #{|f| f.each_line.map{|l| l.chomp!.split(',')}}\
        @hiscore = File.read("hiscore.txt").chomp!
        process_data(@hiscore)
    end

    def process_data(instance)
        @hiscore = @hiscore.split(",").to_a
        @hiscore = @hiscore.each_slice(2).to_a
    end

    def check(score)
        @hiscore.sort!{|s1, s2| s1[0] <=> s2[0]}
        max = @hiscore[4][0].to_i
        if score > max
            puts "Sorry no top score for you."
        else
            add_name(@score.to_s)
            # @hiscore.each do |row|
              # p row[0] do |column|
                  # puts column[0].to_i  
              # end
            # end
        end
    end

    def add_name(score)
        puts "You made it into the Top 5!"
        print "Enter your name: "
        @name = gets.chomp!.to_s
        @hiscore.push([score, @name]).sort!{|s1, s2| s1[0] <=> s2[0]}.pop
        #@hiscore = @scoreList
        #@hiscore = @scoreList
        write_file()

    end

    def write_file()
        File.open('hiscore.txt', 'w') do |f|
        @hiscore.each {|array| f.puts array.join(',')}
            #print "#{@hiscore}"
        end
    end

end

def start
    play = true
    while play == true
        num_guesses = 0
        answer = rand(1..1000)
        puts answer

        @game.show

        loop do
            print "Type in your guess: "
            guess = gets.chomp.to_i

            num_guesses += 1 
            unless guess == answer 
                message = if guess > answer 
                    "Too high"
                else
                    "Too low"
                end
                puts message 
            else
                puts "You got it!"
                puts "It took you #{num_guesses} guesses."
                @score = num_guesses
                @game.check(@score)

                break
            end
        end
        print "Would you like to play again? (y/n): "
        again = gets.chomp!
        if again == 'n'
            play = false
            puts "Ok, Bye!"
            exit
        elsif again == 'y'
            play = true
        end
    end
end

puts "I'm thinking of a random number from 1 to 1000"
puts "Can you guess it?"
@game = HiScore.new()
start()

有人可以帮忙吗？

Answer 1

错误的直接原因是 @hiscore 变量在 process_data 方法中尝试 split-ed 时是 nil。

我猜潜在的错误可能是 read_file 方法中的以下行：

@hiscore = File.read("hiscore.txt").chomp!

根据 documentation，chomp! 方法 returns nil 不对字符串进行修改时 ，即当它不从字符串末尾删除任何换行符时。如果末尾没有换行符，您可能想使用 chomp 而只是 returns 原始字符串。

Answer 2

如果 "hiscore.txt" 的值已经用逗号分隔并且您试图用“,”分隔符再次拆分它，它也可能会引发错误。

“@hiscore”是函数 read_file 的实例变量，因此范围将限于该函数本身。在 "process_data(instance)" 函数中，如果您使用实例代替“@hiscore”并且该变量具有正确的数据，那么它将正确处理。