Ruby:字符串与字符串的比较失败(ArgumentError)

Question

这是我的 ruby 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 firstbook = "Charlie and the Chocolate Factory" 时，secondbook 应该是 "War and Peace" 但代码选择 "Utopia"进行比较。为什么？

Answer 1

确保从传递给 sort! 的 block 中返回比较结果。

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

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
}

一切都会正常进行。

---

题外话，一些吹毛求疵:

• 在Ruby 中，约定是在变量名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。变量 boolean_value 在这里有点误导，因为它不是 true 或 false，它的 -1，0，或 1。