Ruby：字符串与字符串的比较失败（ArgumentError）

Question

这是我的红宝石代码：

books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]

books.sort! {

  |firstBook, secondBook|
  boolean_value = firstBook <=> secondBook
  print "first book is =  '#{firstBook}'"
  print " , second book is = '#{secondBook}'"
  puts  " and there compare result is #{boolean_value}"

}

问题：

1. 此代码运行单次迭代，然后给出错误in 'sort!': comparison of String with String failed (ArgumentError)
2. 当第一本书=“查理和巧克力工厂”时，第二本书应该是“战争与和平”，但它的代码选择“乌托邦”进行比较。为什么？

Answer 1

确保从传递给的块中返回比较结果sort!。

目前，您返回nil（最后一个语句的返回值puts），这会导致不可预测的结果。

将您的代码更改为：

books = ["Charlie and the Chocolate Factory", "War and Peace", "Utopia", "A Brief History of Time", "A Wrinkle in Time"]

books.sort! {

  |firstBook, secondBook|
  boolean_value = firstBook <=> secondBook
  print "first book is =  '#{firstBook}'"
  print " , second book is = '#{secondBook}'"
  puts  " and there compare result is #{boolean_value}"

  boolean_value  # <--- this line has been added
}

一切都会成功。

题外话，说几个小毛病：

• 在 Ruby 中，惯例是在变量名称中用下划线分隔单词。例如，您应该重命名firstBook->first_book
• 命名变量时应该非常小心。该变量boolean_value在这里有点误导，因为它不是trueor false，而是-1, 0, or 1。