Question

我有一个基本的红宝石问题。不久之前做了一些教程，但似乎无法解决这个问题：

class DependencyReader
   @tree
   @dependenciesFromFile

  def read_file
    @tree = {  }
    file = File.new("resources/2.Resource.txt", "r")
    @dependenciesFromFile = Hash.new

    while (line = file.gets)
      splitLine = line.split

      firstLetter = splitLine.shift
      firstLetter.downcase!

      depenendenciesInRow = splitLine
      @dependenciesFromFile[firstLetter] = depenendenciesInRow

    end

    get_tree 'a'
    file.close
  end

  def get_tree(letter)

    unless @tree.has_key? letter
      #add the index to that tree
      @tree[letter] = Array.new
    end

    puts @tree

    @tree.each do |key, value|
      value.push(@dependenciesFromFile[letter])
    end

    puts @dependenciesFromFile
    #prints
    # {"a"=>["B", "C"], "b"=>["C"], "c"=>["D", "E"], "d"=>["F"]}
    puts @dependenciesFromFile["a"]
    #prints nothing

    #gives error
    @dependenciesFromFile["a"].each do |key, value|
      get_tree value
    end

    puts @tree

  end
end

问题出现在这里：

puts @dependenciesFromFile
#prints
# {"a"=>["B", "C"], "b"=>["C"], "c"=>["D", "E"], "d"=>["F"]}
puts @dependenciesFromFile["a"]
#prints nothing

#gives error
@dependenciesFromFile["a"].each do |key, value|
  get_tree value
end

它当然已经填满了，但是当我尝试用字符串作为键来读它时。它没有任何回报。

之后，.each方法会出错，因为它无法循环Nil

编辑：

调用read_file方法的另一个类的代码，该方法调用get_tree方法。

reader = DependencyReader.new

reader.read_file

Answer 1

在包含错误的代码段中，您不应该使用arguments passed而不是"a"，如下所示：

puts @dependenciesFromFile
#prints
# {"a"=>["B", "C"], "b"=>["C"], "c"=>["D", "E"], "d"=>["F"]}
puts @dependenciesFromFile[letter]
#should print a array

#should resolve error
@dependenciesFromFile[letter].each do |key, value|
  get_tree value
end

无法通过密钥ruby读取哈希值

1 个答案: