我无法插入我的哈希，因为它显然是 nil 类？任何人都可以对此有所了解吗？

Question

是否有替代迭代的方法或我可以设置的条件允许我只插入一个哈希的值？我检查了输入的结果，显然当只有一个哈希时，我保存哈希的数组消失了。我还测试了结果，它们属于 Nil 类。

def print_with_index(students)

   students.each_with_index do |student, index|
      index_plus_one = index + 1  
   puts "#{index_plus_one}. #{students[:name]} (#{students[:cohort]} cohort)"

end
end

我如何解决我的问题以及为什么哈希会这样？

完整代码：

def print_header
  puts "The students of Villains Academy"
  puts "--------------"
end

def print_footer(names)
  puts "Overall, we have #{names.count} great students"
end

def input_students
  puts "Please enter the names and then the cohort of the students"
  puts "To finish, just hit return twice"
    #created an empty array
  students = []
    #getting the first name
  name = gets.chomp
  cohort = gets.chomp.to_sym
   if cohort.empty?
    cohort = :november
   end

  if cohort !~ /january|february|march|april|may|june|july|august|september|october|november|december/
  puts "Please enter a valid month"
  puts "Warning months are case sensitive. Please enter in lowercase characters."
    cohort = gets.chomp.to_sym
  end

  while !name.empty? do
     # add the student hash to the array called students
  students << {name: name, cohort: cohort}
    if students.count > 1
       puts "Now we have #{students.count} students"
    else students.count == 1
       puts "Now we have #{students.count} student"
    end
       #getting another name from the user
    name = gets.chomp
    cohort = gets.chomp.to_sym

    if cohort.empty?
     cohort = :november
    end

    if cohort !~ /january|february|march|april|may|june|july|august|september|october|november|december/
    puts "Please enter a valid month"
    puts "Warning months are case sensitive. Please enter in lowercase characters."
    cohort = gets.chomp.to_sym
  end

 end

 bycohort = students.sort_by { |v| v[:cohort] }
  filter = students.select! { |student| student[:cohort] == :november }
 puts bycohort #This allows me to see all of my hashes before they are filtered
 puts ""

 bycohort
 filter
 end

def print_with_index(students)

students.each_with_index do |students, index|
  index_plus_one = index + 1 
  puts "#{index_plus_one}. #{students[:name]} (#{students[:cohort]} cohort)"

   end
  end

### body ###
students = input_students
print_header
print_with_index(students)
print_footer(students)

Answer 1

虽然这对我有用，但我认为使用 each_with_index 枚举，您必须传入一个哈希数组，即 [{...}、{...}、{...}]，而不是单个具有多个键值的哈希

def print_with_index(students)

  students.each_with_index do |students, index|
      index_plus_one = index + 1  
      puts "#{index_plus_one}. #{students[:name]} (#{students[:cohort]} cohort)"
  end
end

print_with_index([{name:"b", cohort: "c"}]) 
# 1. b (c cohort)

Answer 2

您应该使用student 而不是students 作为块参数。您可以检查学生对象是否为nil。

def print_with_index(students)

  students.each_with_index do |student, index|
    if !student.nil?
      index_plus_one = index + 1  
      puts "#{index_plus_one}. #{student[:name]} (#{student[:cohort]}  cohort)"
    end
  end
end